Liquid crystal display device and manufacturing method thereof

ABSTRACT

In a method for manufacturing a liquid crystal display device in which a liquid crystal layer is formed by dropping liquid crystal by a dropping method, a surface of a sealant which is formed over a first substrate is cured by a first cure treatment before dropping the liquid crystal, and then the liquid crystal is dropped. A second substrate has a plurality of projections in a sealant adhesive region. The first substrate and the second substrate are attached to each other with the liquid crystal interposed therebetween so that the plurality of projections is in contact with an uncured region in the sealant formed over the first substrate.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display device and amanufacturing method thereof.

2. Description of the Related Art

In recent years, a liquid crystal display device is used in a wide rangeof fields such as a liquid crystal television, a PDA, a mobile phone,and office automation equipment like a personal computer, as well as aclock and a calculator.

In a liquid crystal display device, liquid crystal is sealed between twosubstrates. When voltage is applied, an orientation of liquid crystalmolecules is changed and light transmittance thereof is changed, so thatan image or the like is displayed optically.

An image quality and reliability of the liquid crystal display deviceare largely affected by whether the two substrates are attached to eachother with good adhesion with the same interval or not. A technique toreduce unevenness of a sealant caused by a wiring which is under thesealant by formation of a dummy wiring and to keep the interval betweenthe substrates has been reported (see Patent Document 1: JapanesePublished Patent Application No. H9-179130).

As a method for forming a liquid crystal layer in the liquid crystaldisplay device, a dipping method in which liquid crystal is injectedwith the use of capillary phenomenon after attachment of a pair ofsubstrates (also referred to as a pumping method or a vacuum injectionmethod) and a liquid crystal dropping method in which liquid crystal issealed by a dropping method are given. Time required for a process canbe shortened and productivity can be improved in a liquid crystaldropping method as compared to a dipping method.

However, when a liquid crystal dropping method is used, since an uncuredsealant and liquid crystal is in contact with each other, there has beena problem in that the liquid crystal is contaminated by the sealant anda sealant with little contamination of liquid crystal has been developed(for example, see Patent Document 2: Japanese Published PatentApplication No. 2005-115255).

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a liquid crystaldisplay device in which deterioration of liquid crystal caused in amanufacturing process is prevented and which has good adhesion betweensubstrates, high reliability and high image quality. It is anotherobject of the present invention to provide a technique by which such aliquid crystal display device with high reliability and high imagequality is manufactured with high productivity.

According to a feature of the present invention, in a liquid crystaldisplay device, a plurality of projections are provided in a sealantadhesive region over a substrate and a pair of substrates are attachedto each other so that the plurality of projections is implanted in thesealant. Since an area in which the sealant is in contact with thesubstrates is increased by the plurality of projections which isimplanted in the sealant, a pair of the substrates are attached morefirmly to each other and adhesion is improved.

A surface of an uncured sealant formed over a first substrate is curedby a first cure treatment before dropping liquid crystal in a method formanufacturing a liquid crystal display device in which the liquidcrystal is dropped by a dropping method to form the liquid crystallayer. After dropping the liquid crystal, the first substrate and thesecond substrate are attached to each other with the liquid crystalinterposed therebetween. Then, the sealant is subjected to a second curetreatment to be cured wholly. In the present invention, the secondsubstrate has the plurality of projections in a sealant adhesive region.The first substrate and the second substrate are attached to each otherwith the liquid crystal interposed therebetween so that the plurality ofprojections is implanted in the sealant formed over the first substrate.

Since a surface of the sealant is cured by the first cure treatment(also referred to as a temporary cure treatment), the liquid crystal isnot in contact with the uncured sealant. Accordingly, contamination ofthe liquid crystal due to the uncured sealant can be prevented.Therefore, reduction in reliability of the liquid crystal display devicecaused by deterioration of the liquid crystal can be prevented and ahigh quality image with reduced display unevenness and a reduced displaydefect can be displayed. In the present invention, the first curetreatment by which the surface of the sealant is cured is to lowerreactivity of a region of the sealant which is in contact with theliquid crystal and to inactivate the region at least as compared to anuncured sealant right after formation of the sealant. Accordingly, atleast the surface of the sealant which is in contact with the liquidcrystal is cured and reactivity to the liquid crystal is lowered by thefirst cure treatment.

Although reactivity of the sealant to the liquid crystal can be loweredin curing the sealant, adhesion with a counter substrate to be attachedis also lowered. In the present invention, the surface of the sealant iscured by the first cure treatment; however, an inside of the sealant isstill in an uncured state in which adhesiveness is high. Since a sealantadhesive region of the second substrate is provided with the pluralityof projections, when the first substrate and the second substrate areattached to each other, the plurality of projections is implanted in thesealant. The projections physically destroy the surface of the sealantof which adhesiveness is lowered by cure treatment and penetrate theinside of the sealant, so that the projections can be in contact withthe uncured sealant with high adhesiveness. Accordingly, the second curetreatment is performed in a state where the plurality of projections isimplanted in the sealant and the sealant is wholly cured, whereby thefirst substrate and the second substrate can be attached firmly to eachother and can stick to each other. Adhesiveness between the firstsubstrate and the second substrate can be improved and reliability ofthe liquid crystal display device can be improved.

Deterioration of the liquid crystal which is caused in the manufacturingprocess of the liquid crystal display device of the present inventioncan be prevented and the liquid crystal display device can have goodadhesion between substrates and high reliability and display ahigh-quality image. Further, such a liquid crystal display device whichhas high reliability and displays a high-quality image can bemanufactured with high productivity.

In the present invention, a cure treatment is performed at least twiceor more; the first cure treatment is a treatment in which only thesurface of the sealant is cured and the second cure treatment is atreatment in which the sealant is wholly cured in a state where theprojections are implanted in the sealant. Each of the first curetreatment and the second cure treatment may be performed once or aplurality of times. As for the method for cure treatment, the sametreatment may be performed (for example, light irradiation treatment isperformed twice) or the different treatments may be performed (forexample, the first is light irradiation treatment and the second is heattreatment) in the cure treatments.

As the cure treatment, light irradiation treatment using ultravioletrays, or the like or heat treatment may be performed. When anultraviolet curing resin is used as the sealant, the ultraviolet curingresin is cured by an ultraviolet irradiation treatment. When athermosetting resin is used, heat treatment may be performed. Inaddition, heat treatment may be performed to the ultraviolet curingresin.

The plurality of projections preferably have shapes with a function as awedge so that the projections are easily implanted in the sealant andadhesion between the projections and the sealant is improved. A pyramidshape such as a pointed needle-like shape (e.g. a cone shape and apolygonal pyramid), a triangular pole of which side surface is providedso as to be in contact with the substrate, or the like can be used.

In the present invention, a liquid crystal element is used as a displayelement and can be used for the liquid crystal display device which hasa display function. Note that the display device may also indicate adisplay panel itself where a plurality of pixels including displayelements such as liquid crystal elements and a peripheral drive circuitfor driving the pixels are formed over a substrate. Further, the displaydevice may include a display panel to which a flexible printed circuit(FPC) or a printed wiring board (PWB) having an IC, a resistor, acapacitor, an inductor, or a transistor may be attached. Such a displaydevice may also include an optical sheet such as a polarizing plate or aretardation plate. Furthermore, it may include a backlight unit (whichmay include a light guide plate, a prism sheet, a diffusion sheet, areflective sheet, and a light source (e.g., an LED or a cold-cathodetube)).

As a liquid crystal display device using a liquid crystal element, atransmissive liquid crystal display device, a semi-transmissive liquidcrystal display device and a reflective liquid crystal display devicecan be given.

One aspect of a method for manufacturing a liquid crystal display deviceof the present invention includes the steps of forming a sealant over afirst substrate; curing a surface of the sealant by performing a firstcure treatment to the sealant; dropping liquid crystal to the firstsubstrate; attaching the first substrate and a second substrate of whichsealant adhesive region is provided with a plurality of projections toeach other with the sealant so that the plurality of projections is incontact with an uncured region in the sealant with the liquid crystalinterposed therebetween; and curing the uncured region in the sealant byperforming a second cure treatment to the sealant.

Another aspect of a method for manufacturing a liquid crystal displaydevice of the present invention includes the steps of forming a sealantover a first substrate; curing a surface of the sealant by performing afirst ultraviolet irradiation treatment to the sealant; dropping liquidcrystal to the first substrate; attaching the first substrate and asecond substrate of which sealant adhesive region is provided with theplurality of projections to each other with the sealant so that theplurality of projections is in contact with an uncured region in thesealant with the liquid crystal interposed therebetween;

and curing the uncured region in the sealant by performing a secondultraviolet irradiation treatment to the sealant.

Another aspect of a method for manufacturing a liquid crystal displaydevice of the present invention includes the steps of forming a sealantover a first substrate;

curing a surface of the sealant by performing a first heat treatment tothe sealant; dropping liquid crystal over the first substrate; attachingthe first substrate and a second substrate of which sealant adhesiveregion is provided with the plurality of projections to each other withthe sealant so that the plurality of projections is in contact with anuncured region in the sealant with the liquid crystal interposedtherebetween; and curing the uncured region in the sealant by performinga second heat treatment to the sealant

One aspect of a liquid crystal display device of the present inventionis that a pair of substrates are attached to each other with liquidcrystal interposed therebetween with a sealant, the plurality ofprojections formed over one of a pair of the substrates are implanted inthe sealant and a material of the plurality of projections is differentfrom that of a substrate which is provided with the plurality ofprojections.

Another aspect of a liquid crystal display device of the presentinvention is that the liquid crystal display device includes a pixelregion where a spacer is provided and an sealant adhesive region whichis provided with the plurality of projections, a pair of substrates areattached to each other with liquid crystal interposed therebetween usingthe sealant, a plurality of projections formed over one of a pair of thesubstrates are implanted in the sealant and a material of the pluralityof projections is different from that of a substrate which is providedwith the plurality of projections.

In the above structure, in the case of a transmissive liquid crystaldisplay device using a light source (e.g. backlight), a pair of thelight-transmitting substrates (the first substrate and the secondsubstrate) are used and light from a light source may be transmitted toa viewing side. On the other hand, in the case of a reflective liquidcrystal display device, one of electrodes with which a pair of thesubstrates (the first substrate and the second substrate) are providedmay have a reflective property. For example, a material having areflective property may be used for a pixel electrode layer.

The liquid crystal may be dropped to an element substrate over which asemiconductor element, and the like are formed or a counter substrate. Aprocess of attaching may be conducted under a reduced pressure. Notethat the liquid crystal may be dropped to the substrate over which thesealant is formed or the substrate over which the plurality ofprojections is formed. Further, in dropping the liquid crystal, theliquid crystal may be heated and the viscosity of the liquid crystal maybe lowered. After attaching the substrates to each other and curing thesealant, heat treatment may be performed. Orientation disorder of theliquid crystal can be corrected by heat treatment.

Since a surface of the sealant is cured by the first cure treatment(also referred to as a temporary cure treatment) before dropping theliquid crystal in the present invention, the liquid crystal is not incontact with the uncured sealant. Accordingly, contamination of theliquid crystal due to the uncured sealant can be prevented. Therefore,reduction in reliability of the liquid crystal display device caused bydeterioration of the liquid crystal can be prevented. The liquid crystaldisplay device with reduced display unevenness, a reduced display defectand high image quality can be realized.

The plurality of projections is provided in an sealant adhesive regionin the second substrate and the plurality of projections is implanted inthe sealant, so that the first substrate and the second substrate areattached to each other. The plurality of projections physically destroythe surface of the sealant of which adhesiveness is lowered by curetreatment and penetrate the inside of the sealant, so that theprojections can be in contact with the uncured sealant with highadhesiveness. Accordingly, the second cure treatment is performed in astate where the plurality of projections is implanted in the sealant andthe sealant is wholly cured, whereby the first substrate and the secondsubstrate can be attached firmly to each other and can stick to eachother.

Accordingly, in the liquid crystal display device of the presentinvention, deterioration of the liquid crystal which is caused in amanufacturing process can be prevented. Further, the liquid crystaldisplay device with good adhesion between substrates, high reliabilityand high image quality can be realized. Moreover, by the presentinvention, such a liquid crystal display device which has highreliability and displays a high-quality image can be manufactured withhigh productivity.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIGS. 1A-1 to 1E-2 are conceptual views of the present invention;

FIGS. 2A to 2D are views each illustrating an example of a projectionwhich can be applied to the present invention;

FIGS. 3A to 3D are views each illustrating an example of forming aprojection which can be applied to the present invention;

FIGS. 4A to 4C are views each illustrating an example of a projectionwhich can be applied to the present invention;

FIGS. 5A and 513 are a top view and a cross sectional view illustratinga liquid crystal display device of the present invention, respectively;

FIGS. 6A and 6B are a top view and a cross sectional view illustrating aliquid crystal display device of the present invention, respectively;

FIG. 7 is a cross sectional view illustrating a liquid crystal displaydevice of the present invention;

FIGS. 8A and 8B are a top view and a cross sectional view illustrating aliquid crystal display device of the present invention, respectively;

FIG. 9 is a cross sectional view illustrating a liquid crystal displaydevice of the present invention;

FIGS. 10A and 10B are cross sectional views illustrating a liquidcrystal display module of the present invention;

FIGS. 11A to 11D are views illustrating a backlight which can be used asa liquid crystal display device of the present invention;

FIGS. 12A to 12C are top views illustrating a liquid crystal displaydevice of the present invention;

FIGS. 13A and 13B are top views illustrating a liquid crystal displaydevice of the present invention;

FIGS. 14A to 14C are block diagrams illustrating a liquid crystaldisplay device of the present invention;

FIG. 15 is a block diagram illustrating a main structure of anelectronic appliance to which the present invention is applied;

FIGS. 16A and 16B are views each illustrating an electronic appliance ofthe present invention;

FIGS. 17A to 17F are views each illustrating an electronic appliance ofthe present invention; and

FIG. 18 is a view illustrating an example of a liquid crystal droppingmethod which can be applied to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiment modes of the present invention will be describedwith reference to the accompanying drawings. However, it is easilyunderstood by a person skilled in the art that the present invention canbe carried out in many different modes, and the mode and the detail ofthe present invention can be variously changed without departing fromthe spirit and the scope thereof. Therefore, the present invention isnot interpreted as being limited to the description of the followingembodiment modes. Note that the same reference numeral may be used todenote the same portions or portions having similar functions indifferent diagrams for explaining the structure of the embodiment modeswith reference to drawings, and repetitive explanation thereof isomitted.

Embodiment Mode 1

In this embodiment mode, an example of a liquid crystal display devicein which deterioration of liquid crystal caused in a manufacturingprocess is prevented and which has higher reliability, higher imagequality, and good adhesion between substrates, and the manufacturingmethod thereof will be described.

FIGS. 1A-1 to 1E-2 illustrate a method for manufacturing a liquidcrystal display device in this embodiment mode using the presentinvention. FIGS. 1A-2 to 1E-2 are top views of a liquid crystal displaydevice in this embodiment mode. FIGS. 1A-1 to 1E-1 are cross sectionalviews taken along lines Y-Z of FIGS. 1A-2 to 1E-2, respectively.

In FIGS. 1A-1 and 1A-2, an uncured sealant 51 (51 a and 51 b) is formedto have a frame-shaped seal pattern over a first substrate 50. In thisembodiment mode, an example is described in which an ultraviolet curingresin is used as the sealant 51; therefore, the sealant 51 (51 a and 51b) is irradiated with ultraviolet rays (also referred to as ultravioletlight) 54 from a light source 53, and only a surface of the sealant 51(51 a and 51 b) is cured as a first cure treatment. As illustrated inFIG. 1B-1 and 1B-2, the sealant 51 (51 a and 51 b) is to be a sealant 65(65 a and 65 b) of which surface is a cured region 52 (52 a and 52 b) byirradiation with ultraviolet rays 54 and of which inside is an uncuredregion (60 a and 60 b).

In the present invention, in the first cure treatment, the sealant isnot wholly cured. The cure treatment is performed such that the uncuredregion remains inside the sealant. Accordingly, the surface of thesealant 65 (65 a and 65 b) is to be the cured region 52 (52 a and 52 b),and the inside of the sealant 65 (65 a and 65 b) is kept the uncuredregion 60 a and 60 b. Since the reactivity of the cured region 52 (52 aand 52 b) with other substances is lowered due to being cured, even ifthe cured region 52 (52 a and 52 b) is in contact with liquid crystal,the cured region 52 (52 a and 52 b) does not easily react with theliquid crystal. The cured region 52 (52 a and 52 b) can blockcontaminant (such as solvent or gas) which is discharged from thesealant to the liquid crystal and can prevent contamination of theliquid crystal. Accordingly, deterioration of the liquid crystal by thesealant can be prevented. In this embodiment mode, irradiation withultraviolet rays is performed from above of the sealant 51 and the curetreatment is performed to the whole surface of the sealant 51. Only asurface of the sealant 51 which is in contact with the liquid crystalmay be cured as selected.

Liquid crystal 56 is dropped from a drop device 55 into the seal patternof the sealant 65 (see FIGS. 1C-1 and 1C-2). Next, the first substrate50 and a second substrate are attached to each other with the liquidcrystal interposed therebetween (see FIGS. 1D-1 and ID-2). A pluralityof projections 58 a and 58 b are provided in a sealant adhesive regionof the second substrate 57. The plurality of projections 58 a and 58 bare examples of those having a pointed needle shape. The secondsubstrate 57 is attached to the first substrate 50 such that theprojections 58 a and 58 b penetrate the cured region 52 (52 a and 52 b)in the sealant 65 and enter the uncured region 60 (60 a and 60 b) insidethe sealant 65. The shape of the sealant 65 is changed by pressing ofthe second substrate 57 to be a sealant 61 (61 a and 61 b), and theliquid crystal spreads so as to fill the inside of the seal pattern. Inthis embodiment mode, since a surface of the sealant 61 (61 a and 61 b)is a cured region, even if the surface of the sealant 61 (61 a and 61 b)is in contact with the liquid crystal, the sealant does not have a badinfluence on the liquid crystal. Further, the second substrate 57 can bein contact with the uncured region with high adhesion using theplurality of projections 58 a and 58 b.

A second cure treatment is performed in a state where the plurality ofprojections 58 a and 58 b are implanted in the sealant 61, so that thesealant 61 is wholly cured. In this embodiment mode, an ultravioletirradiation treatment is performed as the second cure treatment. Thesealan 61 (61 a and 61 b) is irradiated with ultraviolet rays 64 from alight source 63, so that the uncured region in the sealant 61 (61 a and61 b) is cured and a sealant 59 which is cured as a whole is made (seeFIGS. 1E-1 and 1E-2).

Accordingly, the second cure treatment is performed in a state where theplurality of projections 58 a and 58 b are implanted in the sealant 61(61 a and 61 b), the sealant is wholly cured to make the sealant 59,whereby the first substrate 50 and the second substrate 57 can beattached firmly and can stick to each other. Accordingly, adhesionbetween the first substrate 50 and the second substrate 57 can beimproved, and reliability of the liquid crystal display device can beimproved.

In this embodiment mode, cure treatment is performed at least twice ormore; the first cure treatment is treatment in which only the surface ofthe sealant is cured, and the second cure treatment is treatment inwhich the sealant is wholly cured in a state where the projections areimplanted in the sealant. Each of the first cure treatment and thesecond cure treatment may be performed once or a plurality of times. Thesame treatment may be performed (for example, light irradiationtreatment is performed twice) or the different treatments may beperformed (for example, the first is light irradiation treatment and thesecond is heat treatment) as the cure treatments.

As the cure treatment, light irradiation treatment using ultravioletrays, or the like or heat treatment may be performed. When anultraviolet curing resin is used as the sealant, the ultraviolet curingresin is cured by an ultraviolet irradiation treatment. When athermosetting resin is used, heat treatment may be performed. Inaddition, heat treatment may be performed to the ultraviolet curingresin. Light for light irradiation may be light emitted from a lamp orlaser light. A method and conditions (energy, time, pressure,atmosphere, and the like) of an irradiation treatment may be set asappropriate in accordance with a material used for the sealant. Further,a method and conditions (temperature, time, pressure, atmosphere, andthe like) of heat treatment may also be set as appropriate in accordancewith a property of the sealant.

The projections physically destroy the cured region of the surface ofthe sealant. It is acceptable as long as the projections have strengthand height with which the projections can reach the uncured regioninside the sealant, and there is no particular limitation on a materialand a shape used for the projections. The projections preferably haveshapes with a function as a wedge so that the projections are easilyimplanted in the sealant and adhesion between the projections and thesealant is increased, A pyramid shape such as a pointed needle-likeshape (e.g. a cone shape and a polygonal pyramid), a triangular pole ofwhich side surface is provided so as to be in contact with thesubstrate, or the like can be used.

The projections may have a conical shape, a polygonal pyramid (such as atriangular pyramid, quadrangular pyramid, pentagonal pyramid, orsix-sided pyramid) shape, a needle-like shape, a shape of a projectionwith its apex cut off by a plane parallel to its base, a dome shape witha rounded top, or the like. FIGS. 2A to 2D illustrate examples of theshapes of the projections. FIGS. 2A to 2D illustrate cross sections of asurface parallel to a width direction of the sealant, like theprojections 58 a and 58 b illustrated in FIGS. 1D-1 and 1E-1. FIG. 2Aillustrates a projection 801 provided over a substrate 800. Theprojection 801 has a shape having an upper base and a lower base, not apointed shape like a pyramid shape. Therefore, a cross-section on aplane perpendicular to the lower base is trapezoidal. FIG. 2Billustrates an example in which a projection 802 having a rounded top isprovided over the substrate 800. In this manner, the projection may havea shape with a rounded top and a curvature. FIG. 2C illustrates anexample in which a projection 803 where a pyramid shape is stacked on acolumnar shape is provided over the substrate 800. FIG. 2D illustrates aprojection of which top is divided into a plurality of parts.

FIGS. 4A to 4C are perspective views each illustrating an example of ashape of the projection except a pyramid shape. Note that the sealantadhesive region is illustrated as a region 815 in FIGS. 4A to 4C. FIG.4A illustrates a projection 810 with a triangular pole shape of whichside surface is in contact with the substrate. FIG. 4B illustrates aprojection illustrated in FIG. 4A of which top is divided into aplurality of parts and which has a groove. FIG. 4C illustratesprojections 812 a, 812 b and 812 c with triangular pole shapes which areprovided in a different direction from that of the projection 810illustrated in FIG. 4A with respect to the sealant. In this manner, theprojections may be formed so that they can be implanted in the sealantand can have various shapes.

FIGS. 3A to 3D illustrate examples of other shapes and arrangement of aplurality of projections. In FIGS. 3A to 3D, the projections areprovided in a sealant adhesive region 853 over a substrate 850. FIG. 3Aillustrates a projection 852 with a triangular pole shape of which sidesurface is in contact with the substrate 850 as illustrated in FIG. 4A.In FIG. 3A, each projection is provided for each of four sides of thesubstrate. FIG. 3B illustrates an example in which a plurality ofprojections 854 a and 854 b having different shapes are provided. Theprojection 854 a has a shape of a quadrangular pyramid and theprojection 854 b has a triangular pole shape and is provided so that aside surface of the projection 854 b is in contact with the substrate850 as illustrated in FIG. 4A. FIG. 3C illustrates an example in which aplurality of projections 856 a and 856 b having different shapes areprovided. The plurality of projections 856 a with a shape of aquadrangular pyramid and the projections 856 b with a conical shape areprovided. FIG. 3D illustrates an example in which a plurality of minuteprojections 857 with a needle-like shape are provided in the sealantadhesive region. Since the projections needs to be formed so as to avoida region in which an external terminal for electrically connecting tothe outside is formed, when the plurality of projections is formed inthe entire sealant adhesive region as illustrated in FIG. 3D, theprojections are formed with intervals so as to avoid the region in whichan external terminal is formed. The projections may be formed asappropriate so that positions where the external terminal and theprojections are formed are not overlapped each other depending on theposition where the external terminal is formed or the shape of theprojection.

The projections may be formed using the same material as a component ofthe liquid crystal display device and in the same manufacturing processas the liquid crystal display device. Further, only the projections maybe formed in a different process.

Further, asperity may be formed so that the function of the projectionas a wedge can be improved by processing a surface of the projection.When the projection has an anchor effect of functioning as a wedge, thefirst substrate and the second substrate can be attached more firmly.The asperity may be formed by addition of physical force or impact tothe projection. The projection may be changed partially (being dissolvedpartially, or the like) by a chemical treatment (corrosion, or the likeof a surface by a solution with a corrosion effect) or heating to formthe asperity.

The plurality of projections may be formed by processing the substrateor may also be formed over the substrate by formation of a film, or thelike. In addition, the projections may be formed in a different processand attached to the substrate with an adhesive agent, or the like. As asubstrate over which the projections are provided, a glass substrate, aquartz substrate, or the like can be used. A flexible substrate may alsobe used. The flexible substrate indicates a substrate that can be bent.As the flexible substrate, a high-molecular material elastomer, whichcan be processed to be shaped similarly to plastic by plasticization athigh temperature, and has a property such as an elastic body like rubberat room temperature, or the like can be given in addition to a plasticsubstrate made of polycarbonate, polyarylate, polyethersulfone, or thelike. Alternatively, a film (made of polypropylene, polyester, vinyl,polyvinyl fluoride, vinyl chloride, or the like) or an inorganic vapordeposition film can be used. In this manner, the liquid crystal displaydevice of the present invention can be formed employing various shapeshaving the plurality of projections.

A material for forming the projection may be an inorganic material or anorganic material and may be an insulating material or a conductivematerial. For example, as a material for forming the projection,silicon, nitrogen, fluorine, oxide, nitride, fluoride, or the like canbe used. As oxide, the following can be used: silicon oxide, boricoxide, sodium oxide, magnesium oxide, aluminum oxide (alumina),potassium oxide, calcium oxide, diarsenic trioxide (arsenious oxide),strontium oxide, antimony oxide, barium oxide, indium tin oxide (ITO),zinc oxide (ZnO), indium zinc oxide (IZO) in which zinc oxide (ZnO) ismixed in indium oxide, a conductive material in which silicon oxide ismixed in indium oxide, organic indium, organic tin, indium oxidecontaining tungsten oxide, indium zinc oxide containing tungsten oxide,indium oxide containing titanium oxide, indium tin oxide containingtitanium oxide, or the like. As the nitride, aluminum nitride, siliconnitride, or the like can be used. As the fluoride, lithium fluoride,sodium fluoride, magnesium fluoride, calcium fluoride, lanthanumfluoride, or the like can be used. The material used for the projectionsmay include one or more kinds of the above-described silicon, nitrogen,fluorine, oxide, nitride, and fluoride. The above-described materialsused for the substrate can also be used.

As other materials used for the projection, a high molecule such aspolyimide, aromatic polyamide, or polybenzimidazole; or a siloxane resinmay be used. Alternatively, a resin material such as a vinyl resin likepolyvinyl alcohol or polyvinylbutyral, an epoxy resin, a phenol resin, anovolac resin, an acrylic resin, a melamine resin, or a urethane resin,or the like may be used. In addition, metal such as Ag, Au, Cu, Ni, Pt,Pd, Ir, Rh, W, or Al, metal sulfide such as Cd or Zn, an oxide of Fe,Ti, Si, Ge, Zr, Ba, or the like, or a mixture of the materials may alsobe used.

The plurality of projections can be formed in a manner such that a thinfilm is formed by a sputtering method, a vacuum evaporation method, aPVD (physical vapor deposition) method, or a CVD (Chemical VaporDeposition) method such as a low-pressure CVD (LPCVD) method or a plasmaCVD method, and then etched into a desired shape. Alternatively, adroplet discharging method by which a pattern can be formed as selected,a printing method by which a pattern can be transferred or drawn (amethod for forming a pattern such as screen printing or offsetprinting), a coating method, such as a spin coating method, a dippingmethod, a dispenser method, a brush coating method, a spraying method, aflow coating method, or the like can be employed. Still alternatively,an imprinting technique or a nanoimprinting technique with which ananoscale three-dimensional structure can be formed by a transfertechnology can be employed. Imprinting and nanoimprinting are techniquesfor forming a minute three-dimensional structure without using aphotolithography process.

A spacer which controls a distance between the first substrate and thesecond substrate may be formed in a pixel region and a sealant formationregion of the first substrate and the second substrate.

A liquid crystal dropping method employing a dispenser method, which canbe used in the present invention, will be described with reference toFIG. 18. The liquid crystal dropping method illustrated in FIG. 18includes a control device 40, an imaging unit 42, a head 43, a heater44, liquid crystal 33, markers 35 and 45, an insulating layer 34 whichis an alignment film, a sealant 32, the first substrate 20, and thesecond substrate 30. The plurality of projections 25 is formed in asealant adhesive region of the second substrate 30. The sealant 32 has acured region on a surface thereof and has an uncured region inside. Theuncured sealant is formed in a frame-shaped seal pattern, and only thesurface of the sealant is cured by the first cure treatment to form thesealant. The liquid crystal 33 is dropped in the seal pattern having aframe-shape from the head 43. When the viscosity of the liquid crystal33 to be dropped is high, the liquid crystal 33 is heated by the heater44 and the viscosity thereof is adjusted, whereby the liquid crystal 33can be dropped. The first substrate 20 and the second substrate 30 areattached to each other so that the plurality of projections 25 isimplanted in the sealant 32. The liquid crystal is filled with, and thesealant 32 is wholly cured to form a liquid crystal layer.

After the first substrate and the second substrate are attached to eachother with the filled liquid crystal layer interposed therebetween, thesealant is cured and preferably subjected to heat treatment. By heattreatment, the sealant is further cured, so that the adhesive strengthcan be improved and orientation disorder of the liquid crystal can becorrected. A process of attaching is preferably conducted under areduced pressure.

As the sealant, typically, a material containing a visible light curableresin, an ultraviolet curable resin, or a thermosetting resin can beused. For example, an epoxy resin such as a bisphenol-A liquid resin, abisphenol-A solid resin, a bromine-containing epoxy resin, a bisphenol-Fresin, a bisphenol-AD resin, a phenol resin, a cresol resin, a novolacresin, a cycloaliphatic epoxy resin, an Epi-Bis type epoxy resin, aglycidyl ester resin, a glycidyl amine resin, a heterocyclic epoxyresin, or a modified epoxy resin can be used. The uncured sealant can beformed using a droplet discharging method by which a pattern can beformed as selected, a printing method by which a pattern can betransferred or drawn (a method for forming a pattern, such as screenprinting or offset printing), a dispenser method, or the like.

In FIGS. 1A-1 to 1E-2, as the first substrate 50 and the secondsubstrate 57, a glass substrate, a quartz substrate, or the like can beused. A flexible substrate can also be used. The flexible substrateindicates a substrate that can be bent. As the flexible substrate, ahigh-molecular material elastomer, which can be processed to be shapedsimilarly to plastic by plasticization at high temperature, and has aproperty such as an elastic body like rubber at room temperature, or thelike can be given in addition to a plastic substrate made ofpolycarbonate, polyarylate, polyethersulfone, or the like.

Alternatively, a film (made of polypropylene, polyester, vinyl,polyvinyl fluoride, vinyl chloride, or the like) or an inorganic vapordeposition film can be used.

When an alignment film is used, the insulating layer serving as analignment film can be formed using polyimide, polyamide, or the like.The insulating layer can serve as an alignment film by being subjectedto rubbing treatment, but it is not limited as long as the insulatinglayer can serve as an alignment film which aligns liquid crystalmolecules in one direction. Light irradiation or heat treatment may beperformed on the insulating layer to form an alignment film.

Although not illustrated in FIGS. 1A-1 to 1E-2, the first substrate 50and the second substrate 57 are provided with electrode layers to be apixel electrode layer and a counter electrode layer. The electrode layerto be the pixel electrode layer or the counter electrode layer can beformed using one or more kinds of indium tin oxide (ITO), IZO (indiumzinc oxide) which is obtained by mixing indium oxide with zinc oxide(ZnO), or a conductive material which is obtained by mixing indium oxideand silicon oxide (SiO₂); organic indium; organotin; indium oxidecontaining tungsten oxide; indium zinc oxide containing tungsten oxide;indium oxide containing titanium oxide; indium tin oxide containingtitanium oxide; a metal such as tungsten (W), molybdenum (Mo), zirconium(Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium(Cr), cobalt (Co), nickel (Ni), titanium (Ti), platinum (Pt), aluminum(Al), copper (Cu), or silver (Ag); an alloy of the metal; or nitride ofthe metal.

The pixel electrode layer, the counter electrode layer, the insulatinglayer, or the like can be formed in a manner such that a thin film isformed by a sputtering method, a vacuum evaporation method, a PVD(physical vapor deposition) method, or a CVD (Chemical Vapor Deposition)method such as a low-pressure CVD (LPCVD) method or a plasma CVD method,and then etched into a desired shape. Alternatively, a dropletdischarging method by which a pattern can be formed as selected, aprinting method by which a pattern can be transferred or drawn (a methodfor forming a pattern such as screen printing or offset printing), acoating method, such as a spin coating method, a dipping method, adispenser method, a brush coating method, a spraying method, a flowcoating method, or the like can be employed. Still alternatively, animprinting technique or a nanoimprinting technique with which ananoscale three-dimensional structure can be formed by a transfertechnology can be employed. Imprinting and nanoimprinting are techniquesfor forming a minute three-dimensional structure without using aphotolithography process.

In the case of a transmissive liquid crystal display device, a lighttransmitting conductive material may be used for the pixel electrodelayer and the counter electrode layer. On the other hand, in the case ofa reflective liquid crystal display device, a reflective layer may beadditionally provided. Alternatively, a reflective conductive materialis used for the pixel electrode layer and a light transmittingconductive material is used for the counter electrode layer so thatlight reflected by the pixel electrode layer passes through the counterelectrode layer and is emitted from the viewing side.

In the case of the transmissive liquid crystal display device, abacklight, a sidelight, or the like may be used as a light source. Inthe case of the reflective liquid crystal display device, a polarizingplate is provided over a substrate of the viewing side.

In the case of the transmissive liquid crystal display device, astructure is employed in which polarizing plates are provided over afirst substrate side and a second substrate side with a liquid crystallayer interposed therebetween. An optical film such as a retardationplate or an anti-reflection film, or the like may be provided inaddition to the polarizing plate.

In this embodiment mode, an example is described in which the sealant isformed over the first substrate 50, the liquid crystal is dropped andthe second substrate 57 is attached to the first substrate. When anelement substrate provided with a semiconductor element such as a thinfilm transistor is used, the liquid crystal may be dropped to theelement substrate. Alternatively, the sealant may be provided for acounter substrate provided with a color filter, a black matrix, or thelike and the liquid crystal may be dropped to the counter substrate.Accordingly, the first substrate 50 may be the element substrate and thesecond substrate 57 may be the counter substrate, or the first substrate50 may be the counter substrate and the second substrate 57 may be theelement substrate. The liquid crystal may be dropped to the substrateover which the sealant is formed or the substrate over which theplurality of projections is formed.

When the liquid crystal is dropped to the substrate over which theplurality of projections is formed, the viscosity or a dropping positionof the liquid crystal may be set so that the liquid crystal does notspread outside the sealant adhesive region and does not leak outside thesubstrate.

Accordingly, in the liquid crystal display device of this embodimentmode using the present invention, deterioration of the liquid crystalwhich is caused in a manufacturing process can be prevented. Further,the liquid crystal display device with good adhesion between substrates,high reliability and high image quality can be realized. Moreover, sucha liquid crystal display device which has high reliability and displaysa high-quality image can be manufactured with high productivity.

Embodiment Mode 2

In this embodiment mode, an example of a liquid crystal display devicein which deterioration of liquid crystal caused in a manufacturingprocess is prevented and which has higher reliability, higher imagequality, and good adhesion between substrates, and the manufacturingmethod thereof will be described. Specifically, a case in which astructure of the liquid crystal display device is a passive matrix typewill be described.

FIGS. 5A and 5B illustrate a passive matrix liquid crystal displaydevice in this embodiment mode using the present invention. FIG. 5A is atop view of the liquid crystal display device, and FIG. 5B is a crosssectional view taken along a line A-B in FIG. 5A. In FIG. 5A, aninsulating layer 1704 serving as an alignment film, a colored layer1706, a counter substrate 1710, a polarizing plate 1714, and the likeare omitted and are not illustrated; however, they are provided asillustrated in FIG. 5B.

In FIGS. 5A and 5B, a substrate 1700 provided with pixel electrodelayers 1701 a, 1701 b and 1701 c which extend in a first direction andan insulating layer 1712 serving as an alignment film faces a substrate1710 provided with an insulating layer 1704 serving as an alignmentfilm, counter electrode layers 1705 a, 1705 b and 1705 c which extend ina second direction perpendicular to the first direction, a colored layer1706 serving as a color filter and a polarizing plate 1714 with a liquidcrystal layer 1703 interposed therebetween (see FIGS. 5A and 5B). Thealignment film indicates an insulating layer in which molecules at itssurface are made aligned by rubbing treatment or the like.

Similarly to Embodiment Mode 1, in this embodiment mode using thepresent invention, with respect to a method for manufacturing a liquidcrystal display device in which liquid crystal is dropped by a droppingmethod to form the liquid crystal layer, a surface of an uncured sealantformed over a first substrate (the substrate 1700 or the substrate 1710)is cured by a first cure treatment before dropping the liquid crystal.After dropping the liquid crystal, the first substrate (the substrate1700 or the substrate 1710) and the second substrate (the substrate 1700or the substrate 1710) are attached to each other with the liquidcrystal interposed therebetween. Then, the sealant is subjected to asecond cure treatment to be cured wholly. In this embodiment mode, thesecond substrate (the substrate 1700 or the substrate 1710) has aplurality of projections in an sealant adhesive region. The firstsubstrate (the substrate 1700 or the substrate 1710) and the secondsubstrate (the substrate 1700 or the substrate 1710) are attached toeach other with the liquid crystal interposed therebetween so that theplurality of projections is implanted in the sealant formed over thefirst substrate (the substrate 1700 or the substrate 1710).

Since the surface of the sealant is cured by the first cure treatment,the liquid crystal is not in contact with the uncured sealant.Accordingly, contamination of the liquid crystal due to the uncuredsealant can be prevented. Therefore, reduction in reliability of theliquid crystal display device caused by deterioration of the liquidcrystal can be prevented. The liquid crystal display device with reduceddisplay unevenness, a reduced display defect and high image quality canbe realized.

In this embodiment mode, although the surface of the sealant is cured bythe first cure treatment, an inside of the sealant is still in anuncured state in which adhesiveness is high. Since a sealant adhesiveregion of the second substrate (the substrate 1700 or the substrate1710) is provided with the plurality of projections, when the firstsubstrate (the substrate 1700 or the substrate 1710) and the secondsubstrate (the substrate 1700 or the substrate 1710) are attached toeach other, the plurality of projections is implanted in the sealant.The projections physically destroy the surface of the sealant of whichadhesiveness is lowered by cure treatment and penetrate the inside ofthe sealant, so that the projections can be in contact with the uncuredsealant with high adhesiveness. Accordingly, the sealant in which theplurality of projections is implanted is wholly cured by the second curetreatment, whereby the first substrate (the substrate 1700 or thesubstrate 1710) and the second substrate (the substrate 1700 or thesubstrate 1710) can be attached firmly to each other and can stick toeach other Adhesiveness between the first substrate (the substrate 1700or the substrate 1710) and the second substrate (the substrate 1700 orthe substrate 1710) can be improved and reliability of the liquidcrystal display device can be improved.

In this embodiment mode, a cure treatment is performed at least twice ormore; the first cure treatment is treatment in which only the surface ofthe sealant is cured and the second cure treatment is treatment in whichthe sealant is wholly cured in a state where the projections areimplanted in the sealant. Each of the first cure treatment and thesecond cure treatment may be performed once or a plurality of times. Thesame treatment may be performed (for example, light irradiationtreatment is performed twice) and different treatments may be performed(for example, the first is light irradiation treatment and the second isheat treatment) as the cure treatments.

As the cure treatment, light irradiation treatment using ultravioletrays, or the like or heat treatment may be performed. When anultraviolet curing resin is used as the sealant, the ultraviolet curingresin is cured by an ultraviolet irradiation treatment. When athermosetting resin is used, heat treatment may be performed. Inaddition, heat treatment may be performed to the ultraviolet curingresin. Light for light irradiation may be light emitted from a lamp orlaser light. A method and conditions (energy, time, pressure,atmosphere, and the like) of an irradiation treatment may be set asappropriate in accordance with a material used for the sealant. Further,a method and conditions (temperature, time, pressure, atmosphere, andthe like) of heat treatment may also be set as appropriate in accordancewith a property of the sealant.

The projections physically destroy the cured region of the surface ofthe sealant. It is acceptable as long as the projections have strengthand height with which the projections can reach the uncured regioninside the sealant, and there is no particular limitation on a materialand a shape used for the projections. The projections preferably have ashape with a function as a wedge so that the projections are easilyimplanted in the sealant and adhesion between the projections and thesealant is increased. A pyramid shape such as a pointed needle-likeshape (e.g. a cone shape and a polygonal pyramid), a triangular pole ofwhich side surface is provided so as to be in contact with thesubstrate, or the like can be used.

The projections may be formed using the same material as a component ofthe liquid crystal display device and in the same manufacturing processas the liquid crystal display device. Further, only the projections maybe formed in a different process.

Further, asperity may be formed so that the function of the projectionas a wedge can be improved by processing the surface of the projection.When the projection has an anchor effect of functioning as a wedge, thefirst substrate and the second substrate can be attached firmly. Theasperity may be formed by addition of physical force or impact to theprojection. The projection may be changed partially (being dissolvedpartially, or the like) by a chemical treatment (corrosion, or the likeof a surface by a solution with a corrosion effect) or heating to formthe asperity.

The plurality of projections may be formed by processing the substrateor may also be formed over the substrate by formation of a film, or thelike. Alternatively, the projections may be formed in a differentprocess and attached to the substrate with an adhesive agent, or thelike. As a substrate which is provided with the projections, a glasssubstrate or a quartz substrate can be used. A flexible substrate mayalso be used. The flexible substrate indicates a substrate that can bebent. As the flexible substrate, a high-molecular material elastomer,which can be processed to be shaped similarly to plastic byplasticization at high temperature, and has a property such as anelastic body like rubber at room temperature, or the like can be givenin addition to a plastic substrate made of polycarbonate, polyarylate,polyethersulfone, or the like. Alternatively, a film (made ofpolypropylene, polyester, vinyl, polyvinyl fluoride, vinyl chloride, orthe like) or an inorganic vapor deposition film can be used. In thismanner, the liquid crystal display device of the present invention canbe formed employing various shapes having the plurality of projections.

A material for forming the projection may be an inorganic material or anorganic material and may be an insulating material or a conductivematerial. For example, as a material for forming the projection,silicon, nitrogen, fluorine, oxide, nitride, fluoride, or the like canbe used. As oxide, the following can be used: silicon oxide, boricoxide, sodium oxide, magnesium oxide, aluminum oxide (alumina),potassium oxide, calcium oxide, diarsenic trioxide (arsenious oxide),strontium oxide, antimony oxide, barium oxide, indium tin oxide (ITO),zinc oxide (ZnO), indium zinc oxide (IZO) in which zinc oxide (ZnO) ismixed in indium oxide, a conductive material in which silicon oxide ismixed in indium oxide, organic indium, organic tin, indium oxidecontaining tungsten oxide, indium zinc oxide containing tungsten oxide,indium oxide containing titanium oxide, indium tin oxide containingtitanium oxide, or the like. As the nitride, aluminum nitride, siliconnitride, or the like can be used. As the fluoride, lithium fluoride,sodium fluoride, magnesium fluoride, calcium fluoride, lanthanumfluoride, or the like can be used. The material used for the projectionsmay include one or more kinds of the above-described silicon, nitrogen,fluorine, oxide, nitride, and fluoride. The above-described materialsused for the substrate can also be used.

As other materials used for the projection, a high molecule such aspolyimide, aromatic polyamide, or polybenzimidazole; or a siloxane resinmay be used.

Alternatively, a resin material such as a vinyl resin like polyvinylalcohol or polyvinylbutyral, an epoxy resin, a phenol resin, a novolacresin, an acrylic resin, a melamine resin, or a urethane resin, or thelike may be used. In addition, metal such as Ag, Au, Cu, Ni, Pt, Pd, Ir,Rh, W, or Al, metal sulfide of Cd or Zn, an oxide of Fe, Ti, Si, Ge, Zr,Ba, or the like, or a mixture of the materials may also be used.

The plurality of projections can be formed in a manner such that a thinfilm is formed by a sputtering method, a vacuum evaporation method, aPVD (physical vapor deposition) method, or a CVD (Chemical VaporDeposition) method such as a low-pressure CVD (LPCVD) method or a plasmaCVD method, and then etched into a desired shape. Alternatively, adroplet discharging method by which a pattern can be formed as selected,a printing method by which a pattern can be transferred or drawn (amethod for forming a pattern such as screen printing or offsetprinting), a coating method, such as a spin coating method, a dippingmethod, a dispenser method, a brush coating method, a spraying method, aflow coating method, or the like can be employed. Still alternatively,an imprinting technique or a nanoimprinting technique with which ananoscale three-dimensional structure can be formed by a transfertechnology can be employed. Imprinting and nanoimprinting are techniquesfor forming a minute three-dimensional structure without using aphotolithography process.

A spacer which controls a distance between the first substrate and thesecond substrate may be formed in the sealant formation regions of thefirst substrate and the second substrate.

After the first substrate and the second substrate are attached to eachother with the filled liquid crystal layer interposed therebetween, thesealant is preferably cured and subjected to heat treatment. By heattreatment, the sealant is further cured, so that the adhesive strengthcan be improved and orientation disorder of the liquid crystal can becorrected. A process of attaching is preferably conducted under areduced pressure.

As the sealant, typically, a visible light curable resin, an ultravioletcurable resin, or a thermosetting resin can be used. For example, anepoxy resin such as a bisphenol-A liquid resin, a bisphenol-A solidresin, a bromine-containing epoxy resin, a bisphenol-F resin, abisphenol-AD resin, a phenol resin, a cresol resin, a novolac resin, acycloaliphatic epoxy resin, an Epi-Bis type epoxy resin, a glycidylester resin, a glycidyl amine resin, a heterocyclic epoxy resin, or amodified epoxy resin can be used. The uncured sealant can be formedusing a droplet discharging method by which a pattern can be formed asselected, a printing method by which a pattern can be transferred ordrawn (a method for forming a pattern, such as screen printing or offsetprinting), a dispenser method, or the like.

When an element substrate over which a semiconductor element such as athin film transistor is formed is used, the liquid crystal may bedropped to the element substrate. Alternatively, the sealant may beprovided for a counter substrate provided with a color filter, a blackmatrix, or the like and the liquid crystal may be dropped to the countersubstrate. Accordingly, the sealant may be provided for either theelement substrate 1700 or the counter substrate 1710 and the liquidcrystal may be dropped to either the element substrate 1700 or thecounter substrate 1710.

As the substrates 1700 and 1710, a glass substrate, a quartz substrate,or the like can be used. A flexible substrate can also be used. Theflexible substrate indicates a substrate that can be bent. As theflexible substrate, a high-molecular material elastomer, which can beprocessed to be shaped similarly to plastic by plasticization at hightemperature, and has a property such as an elastic body like rubber atroom temperature, or the like can be given in addition to a plasticsubstrate made of polycarbonate, polyarylate, polyethersulfone, or thelike. Alternatively, a film (made of polypropylene, polyester, vinyl,polyvinyl fluoride, vinyl chloride, or the like) or an inorganic vapordeposition film can be used.

The pixel electrode layers 1701 a, 1701 b and 1701 c and the counterelectrode layers 1705 a, 1705 b and 1705 c can be formed using one ormore kinds of a conductive material such as indium tin oxide (ITO), IZO(indium zinc oxide) which is obtained by mixing indium oxide with zincoxide (ZnO), or a mixture of indium oxide and silicon oxide (SiO₂);organic indium; organotin; indium oxide containing tungsten oxide;indium zinc oxide containing tungsten oxide; indium oxide containingtitanium oxide; indium tin oxide containing titanium oxide; a metal suchas tungsten (W), molybdenum (Mo), zirconium (Zr), hafnium (Hf), vanadium(V), niobium (Nb), tantalum (Ta), chromium (Cr), cobalt (Co), nickel(Ni), titanium (Ti), platinum (Pt), aluminum (Al), copper (Cu), orsilver (Ag); an alloy of the metal; or nitride of the metal.

In the case of a transmissive liquid crystal display device, alight-transmitting conductive material may be used for the pixelelectrode layers 1701 a, 1701 b and 1701 c and the counter electrodelayers 1705 a, 1705 b and 1705 c. In the case of a reflective liquidcrystal display device, a reflective layer may be additionally provided.Alternatively, a reflective conductive material is used for the pixelelectrode layers 1701 a, 1701 b and 1701 c, and a light-transmittingconductive material is used for the counter electrode layers 1705 a,1705 b and 1705 c so that light reflected by the pixel electrode layers1701 a, 1701 b and 1701 c passes through the counter electrode layers1705 a, 1705 b and 1705 c and is emitted from the viewing side.

In the case of the transmissive liquid crystal display device, abacklight, a sidelight, or the like may be used as a light source. Inthe case of the transmissive liquid crystal display device, a polarizingplate is also provided outside the substrate 1700.

After forming a conductive layer, an insulating layer, or the like bydischarging a composition by a droplet discharge method, the surfacethereof may be planarized by pressing with pressure to improveplanarity. As a pressing method, unevenness may be reduced by moving aroller-shaped object over the surface, or the surface may be pressedwith a flat plate-shaped object. A heating step may be performed at thetime of pressing. Alternatively, surface unevenness may be eliminatedwith an air knife after softening or melting the surface with a solventor the like. A CMP method may be alternatively used for polishing thesurface. This step may be employed in planarizing the surface whenunevenness is generated by a droplet discharge method.

Accordingly, in the liquid crystal display device of this embodimentmode using the present invention, deterioration of the liquid crystalwhich is caused in a manufacturing process can be prevented. Further,the liquid crystal display device which has good adhesion betweensubstrates and high reliability and high image quality can be realized.Moreover, such a liquid crystal display device with high reliability andhigh image quality can be manufactured with high productivity.

This embodiment mode can be freely combined with Embodiment Mode 1.

Embodiment Mode 3

In this embodiment mode, an example of a liquid crystal display devicein which deterioration of liquid crystal caused in a manufacturingprocess is prevented and which has higher reliability, higher imagequality, and good adhesion between substrates, and the manufacturingmethod thereof will be described. In this embodiment mode, a liquidcrystal display device having a different structure from that describedin Embodiment Mode 2 will be described. Specifically, a case in which astructure of the liquid crystal display device is an active matrix typewill be described.

FIG. 6A is a top view of a liquid crystal display device, and FIG. 6B isa cross sectional view of a liquid crystal display device taken along aline E-F in FIG. 6A. In FIG. 6A, a liquid crystal layer, an alignmentfilm which is provided for a counter substrate side, a counter electrodelayer, a colored layer, and the like are omitted and are notillustrated; however, they are provided as illustrated in FIG. 6B.

First wirings that extend in a first direction and second wirings thatextend in a second direction perpendicular to the first direction areprovided in matrix over a substrate 520 provided with an insulatinglayer 523 as a base film. One of the first wirings is connected to asource electrode or a drain electrode of a transistor 521, and one ofthe second wirings is connected to a gate electrode of the transistor521. A pixel electrode layer 531 is connected to a wiring layer 525 bthat is the source electrode or the drain electrode of the transistor521, which is not connected to the first wiring.

The substrate 520 provided with the transistor 521 which is an inverselystaggered thin film transistor, an insulating layer 557, an insulatinglayer 527, the pixel electrode layer 531 and an insulating layer 561serving as an alignment film; and the substrate 568 provided with aninsulating layer 563 serving as an alignment film, a counter electrodelayer 564, a colored layer 565 serving as a color filter and apolarizing plate (a layer including a polarizer, or simply referred toas a polarizer) 556 face each other with a liquid crystal layer 562interposed therebetween.

Similarly to Embodiment Mode 1, in this embodiment mode using thepresent invention, with respect to a method for manufacturing a liquidcrystal display device in which liquid crystal is dropped by a droppingmethod to form the liquid crystal layer, a surface of an uncured sealantformed over a first substrate (the substrate 520 or the substrate 568)is cured by a first cure treatment before dropping the liquid crystal.

After dropping the liquid crystal, the first substrate (the substrate520 or the substrate 568) and the second substrate (the substrate 520 orthe substrate 568) are attached to each other with the liquid crystalinterposed therebetween. Then, the sealant is subjected to a second curetreatment to be cured wholly. In this embodiment mode, the secondsubstrate (the substrate 520 or the substrate 568) has a plurality ofprojections in a sealant adhesive region. The first substrate (thesubstrate 520 or the substrate 568) and the second substrate (thesubstrate 520 or the substrate 568) are attached to each other with theliquid crystal interposed therebetween so that the plurality ofprojections is implanted in the sealant formed over the first substrate(the substrate 520 or the substrate 568).

Since the surface of the sealant is cured by the first cure treatment,the liquid crystal is not in contact with the uncured sealant.Accordingly, contamination of the liquid crystal due to the uncuredsealant can be prevented. Therefore, reduction in reliability of theliquid crystal display device caused by deterioration of the liquidcrystal can be prevented. The liquid crystal display device with reduceddisplay unevenness, a reduced display defect and high image quality canbe realized.

In this embodiment mode, although the surface of the sealant is cured bythe first cure treatment, the inside of the sealant is still in anuncured state in which adhesiveness is high. Since a sealant adhesiveregion of the second substrate (the substrate 520 or the substrate 568)is provided with the plurality of projections, when the first substrate(the substrate 520 or the substrate 568) and the second substrate (thesubstrate 520 or the substrate 568) are attached to each other, theplurality of projections is implanted in the sealant. The projectionsphysically destroy the surface of the sealant of which adhesiveness islowered by cure treatment and penetrate the inside of the sealant, sothat the projections can be in contact with the uncured sealant withhigh adhesiveness. Accordingly, the sealant in which the plurality ofprojections is implanted is wholly cured by the second cure treatment,whereby the first substrate (the substrate 520 or the substrate 568) andthe second substrate (the substrate 520 or the substrate 568) can beattached firmly to each other and can stick to each other. Adhesivenessbetween the first substrate (the substrate 520 or the substrate 568) andthe second substrate (the substrate 520 or the substrate 568) can beimproved and reliability of the liquid crystal display device can beimproved.

In this embodiment mode, cure treatment is performed at least twice ormore; the first cure treatment is treatment in which only the surface ofthe sealant is cured and the second cure treatment is treatment in whichthe sealant is wholly cured in a state where the projections areimplanted in the sealant. Each of the first cure treatment and thesecond cure treatment may be performed once or a plurality of times. Thesame treatment may be performed (for example, light irradiationtreatment is performed twice) and different treatments may be performed(for example, the first is light irradiation treatment and the second isheat treatment) as the cure treatments.

As the cure treatment, light irradiation treatment using ultravioletrays, or the like or heat treatment may be performed. When anultraviolet curing resin is used as the sealant, the ultraviolet curingresin is cured by an ultraviolet irradiation treatment. When athermosetting resin is used, heat treatment may be performed. Inaddition, heat treatment may be performed to the ultraviolet curingresin. Light for light irradiation may be light emitted from a lamp orlaser light. A method and conditions (energy, time, pressure,atmosphere, and the like) of an irradiation treatment may be set asappropriate in accordance with a material used for the sealant. Further,a method and conditions (temperature, time, pressure, atmosphere, andthe like) of heat treatment may also be set as appropriate in accordancewith a property of the sealant.

The projections physically destroy the cured region of the surface ofthe sealant. It is acceptable as long as the projections have strengthand height with which the projections can reach the uncured regioninside the sealant, and there is no particular limitation on a materialand a shape used for the projections. The projections preferably have ashape with a function as a wedge so that the projections are easilyimplanted in the sealant and adhesion between the projections and thesealant is increased. A pyramid shape such as a pointed needle-likeshape (e.g. a cone shape and a polygonal pyramid), a triangular pole ofwhich side surface is provided so as to be in contact with thesubstrate, or the like can be used.

The projections may be formed using the same material as a component ofthe liquid crystal display device and in the same manufacturing processas the liquid crystal display device. Further, only the projections maybe formed in a different process.

Further, asperity may be formed so that the function of the projectionas a wedge can be improved by processing the surface of the projection.When the projection has an anchor effect of functioning as a wedge, thefirst substrate and the second substrate can be attached more firmly.The asperity may be formed by addition of physical force or impact tothe projection. The projection may be changed partially (being dissolvedpartially, or the like) by a chemical treatment (corrosion, or the likeof a surface by a solution with a corrosion effect) or heating to formthe asperity.

The plurality of projections may be formed by processing the substrateor may also be formed over the substrate by formation of a film, or thelike. Alternatively, the projections may be formed in a differentprocess and attached to the substrate with an adhesive agent, or thelike. As a substrate which is provided with the projections, a glasssubstrate or a quartz substrate can be used. A flexible substrate mayalso be used. The flexible substrate indicates a substrate that can bebent. As the flexible substrate, a high-molecular material elastomer,which can be processed to be shaped similarly to plastic byplasticization at high temperature, and has a property such as anelastic body like rubber at room temperature, or the like can be givenin addition to a plastic substrate made of polycarbonate, polyarylate,polyethersulfone, or the like. Alternatively, a film (made ofpolypropylene, polyester, vinyl, polyvinyl fluoride, vinyl chloride, orthe like) or an inorganic vapor deposition film can be used. In thismanner, the liquid crystal display device of the present invention canbe formed employing various shapes having the plurality of projections.

A material for forming the projection may be an inorganic material or anorganic material and may be an insulating material or a conductivematerial. For example, as a material for forming the projection,silicon, nitrogen, fluorine, oxide, nitride, fluoride, or the like canbe used. As oxide, the following can be used: silicon oxide, boricoxide, sodium oxide, magnesium oxide, aluminum oxide (alumina),potassium oxide, calcium oxide, diarsenic trioxide (arsenious oxide),strontium oxide, antimony oxide, barium oxide, indium tin oxide (ITO),zinc oxide (ZnO), indium zinc oxide (IZO) in which zinc oxide (ZnO) ismixed in indium oxide, a conductive material in which silicon oxide ismixed in indium oxide, organic indium, organic tin, indium oxidecontaining tungsten oxide, indium zinc oxide containing tungsten oxide,indium oxide containing titanium oxide, indium tin oxide containingtitanium oxide, or the like. As the nitride, aluminum nitride, siliconnitride, or the like can be used. As the fluoride, lithium fluoride,sodium fluoride, magnesium fluoride, calcium fluoride, lanthanumfluoride, or the like can be used. The material used for the projectionsmay include one or more kinds of the above-described silicon, nitrogen,fluorine, oxide, nitride, and fluoride. The above-described materialsused for the substrate can also be used.

As other materials used for the projection, a high molecule such aspolyimide, aromatic polyamide, or polybenzimidazole; or a siloxane resinmay be used. Alternatively, a resin material such as a vinyl resin likepolyvinyl alcohol or polyvinylbutyral, an epoxy resin, a phenol resin, anovolac resin, an acrylic resin, a melamine resin, or a urethane resin,or the like may be used. In addition, metal such as Ag, Au, Cu, Ni, Pt,Pd, Ti, Rh, W, or Al, metal sulfide of Cd or Zn, an oxide of Fe, Ti, Si,Ge, Zr, Ba, or the like, or a mixture of the materials may also be used.

The plurality of projections can be formed in a manner such that a thinfilm is formed by a sputtering method, a vacuum evaporation method, aPVD (physical vapor deposition) method, or a CVD (Chemical VaporDeposition) method such as a low-pressure CVD (LPCVD) method or a plasmaCVD method, and then etched into a desired shape. Alternatively, adroplet discharging method by which a pattern can be formed as selected,a printing method by which a pattern can be transferred or drawn (amethod for forming a pattern such as screen printing or offsetprinting), a coating method, such as a spin coating method, a dippingmethod, a dispenser method, a brush coating method, a spraying method, aflow coating method, or the like can be employed. Still alternatively,an imprinting technique or a nanoimprinting technique with which ananoscale three-dimensional structure can be formed by a transfertechnology can be employed. Imprinting and nanoimprinting are techniquesfor forming a minute three-dimensional structure without using aphotolithography process.

A spacer which controls a distance between the first substrate (thesubstrate 520 or the substrate 568) and the second substrate (thesubstrate 520 or the substrate 568) may be formed in the sealantformation regions of the first substrate (the substrate 520 or thesubstrate 568) and the second substrate (the substrate 520 or thesubstrate 568).

After the first substrate (the substrate 520 or the substrate 568) andthe second substrate (the substrate 520 or the substrate 568) areattached to each other with the filled liquid crystal layer 562interposed therebetween, the sealant is preferably cured and subjectedto heat treatment. By heat treatment, the sealant is further cured, sothat the adhesive strength can be improved and orientation disorder ofthe liquid crystal can be corrected. A process of attaching ispreferably conducted under a reduced pressure.

As the sealant, typically, a visible light curable resin, an ultravioletcurable resin, or a thermosetting resin can be used. For example, anepoxy resin such as a bisphenol-A liquid resin, a bisphenol-A solidresin, a bromine-containing epoxy resin, a bisphenol-F resin, abisphenol-AD resin, a phenol resin, a cresol resin, a novolac resin, acycloaliphatic epoxy resin, an Epi-Bis type epoxy resin, a glycidylester resin, a glycidyl amine resin, a heterocyclic epoxy resin, or amodified epoxy resin can be used. The uncured sealant can be formedusing a droplet discharging method by which a pattern can be formed asselected, a printing method by which a pattern can be transferred ordrawn (a method for forming a pattern, such as screen printing or offsetprinting), a dispenser method, or the like.

When an element substrate over which a semiconductor element such as athin film transistor is formed is used, the liquid crystal may bedropped to the element substrate. Alternatively, the sealant may beprovided for a counter substrate provided with a color filter, a blackmatrix, or the like and the liquid crystal may be dropped to the countersubstrate. Accordingly, the sealant may be provided for either theelement substrate 520 or the counter substrate 568 and the liquidcrystal may be dropped to either the element substrate 520 or thecounter substrate 568.

FIGS. 6A and 6B in this embodiment mode illustrate an example in whichthe transistor 521 is a channel-etch inversed-staggered transistor. InFIGS. 6A and 6B, the transistor 521 includes a gate electrode layer 502,a gate insulating layer 526, a semiconductor layer 504, semiconductorlayers 503 a and 503 b having one conductivity type, wiring layers 525 aand 525 b, one of which serves as a source electrode layer and the otheras a drain electrode layer.

FIG. 7 illustrates an example in which a transistor having a multi-gatestructure is used. In FIG. 7, the substrate 520 provided with thetransistor 551 having a multi-gate structure, the pixel electrode layer531 and an insulating layer 561 serving as an alignment film; and thesubstrate 568 provided with an insulating layer 563 serving as analignment film, a counter electrode layer 564, a colored layer 565serving as a color filter and a polarizing plate (a layer including apolarizer, or simply referred to as a polarizer) 556 face each otherwith a liquid crystal layer 562 interposed therebetween.

In FIG. 7, the polarizing plate 556 is provided outside the substrate568 which is a counter substrate. The polarizing plate, the colorfilter, and the like may be provided between the substrates or outsidethe substrates. In FIG. 7, an example of a liquid crystal display devicein which the polarizing plate 556 is provided outside the substrate 568and the colored layer 565 and the counter electrode layer 564 aresequentially provided inside the substrate 568 is illustrated; however,a stacked layer structure of the polarizing plate and the colored layeris not limited to that illustrated in

FIG. 7 and may be set as appropriate depending on materials of thepolarizing plate and the colored layer or conditions of a manufacturingprocess. FIG. 7 illustrates a reflective liquid crystal display device,and one polarizing plate is provided at the counter substrate side whichis a viewing side. In the case of a transmissive liquid crystal displaydevice, both of the element substrate and the counter substrate areprovided with polarizing plates with the liquid crystal layer interposedtherebetween. A retardation plate, or the like may also be providedbetween the polarizing plate and the alignment film and a surface whichis the closest to the viewing side can be provided with an optical filmsuch as an anti-reflection film.

The transistor 551 is an example of a multi-gate channel-etchinversed-staggered transistor. In FIG. 7, the transistor 551 includesgate electrode layers 552 a and 552 b; a gate insulating layer 523; asemiconductor layer 554; semiconductor layers 553 a, 553 b and 553 ceach having one conductivity type; wiring layers 555 a, 555 b and 555 ceach of which is a source electrode layer or a drain electrode layer. Aninsulating layer 557 is provided over the transistor 551.

As a material for forming the semiconductor layer, a polycrystallinesemiconductor formed by crystallizing an amorphous semiconductor(hereinafter also referred to as an “AS”) by utilizing light energy orthermal energy, a single crystalline semiconductor, or the like can beused. The amorphous semiconductor can be manufactured by a vapor phasegrowth method that uses a semiconductor material gas typified by silaneor germane or a sputtering method.

Typical examples of an amorphous semiconductor include hydrogenatedamorphous silicon, and typical examples of a crystalline semiconductorinclude polysilicon and the like. Examples of polysilicon(polycrystalline silicon) include so-called high-temperature polysiliconthat contains polysilicon as a main component and is formed at a processtemperature greater than or equal to 800° C., so-called low-temperaturepolysilicon that contains polysilicon as a main component and is formedat a process temperature less than or equal to 600° C., polysiliconobtained by crystallizing amorphous silicon by using an element thatpromotes crystallization or the like, and the like. Instead of such athin film process, an SOI substrate formed by providing a singlecrystalline semiconductor layer on an insulating surface may be used.The SOI substrate can be formed by an SIMOX (separation by implantedoxygen) method or a Smart-Cut method. In the SIMOX method, oxygen ionsare implanted into a single crystalline silicon substrate to form anoxygen-containing layer at a predetermined depth, and then heattreatment is conducted to form an embedded insulating layer at thepredetermined depth from the surface, thereby forming a singlecrystalline silicon layer over the embedded insulating layer. In theSmart-Cut method, hydrogen ions are implanted into an oxidized singlecrystalline silicon substrate to form a hydrogen-containing layer in aportion corresponding to a desired depth, the oxidized singlecrystalline silicon substrate is attached to a supporting substrate(such as a single crystalline silicon substrate having a silicon oxidefilm for attachment on its surface), and heat treatment is conducted.Accordingly, the single crystalline silicon substrate is separated atthe hydrogen-containing layer, and stack layers of the silicon oxidefilm and the single crystalline silicon layer is formed over thesupporting substrate.

When a crystalline semiconductor film is used for the semiconductorfilm, the crystalline semiconductor layer may be formed by variousmethods such as a laser crystallization method, a thermalcrystallization method, a thermal crystallization method using anelement that promotes crystallization such as nickel, or the like. Amicrocrystalline semiconductor can be crystallized by laser irradiation,whereby crystallinity thereof can be enhanced. When the element thatpromotes crystallization is not added, before an amorphous semiconductorlayer is irradiated with a laser beam, hydrogen contained in theamorphous semiconductor layer is discharged until the concentration ofhydrogen becomes less than or equal to 1×10²⁰ atoms/cm³ by heating theamorphous semiconductor layer at a temperature of 500° C. for one hourin a nitrogen atmosphere. This is because the amorphous semiconductorlayer containing much hydrogen is damaged when irradiated with a laserbeam. The thermal treatment for crystallization can be performed using aheating furnace, laser irradiation, irradiation with light emitted froma lamp (also referred to as lamp annealing), or the like. Examples of aheating method include an RTA method such as a GRTA (gas rapid thermalannealing) method or an LRTA (lamp rapid thermal annealing) method. GRTAis a method of thermal treatment using a high-temperature gas, and LRTAis a method of thermal treatment using light from a lamp.

The crystallization may be performed by adding an element that promotescrystallization (also referred to as a catalyst element or a metalelement) to an amorphous semiconductor layer and applying thermaltreatment (at 550 to 750° C. for 3 minutes to 24 hours) thereto in acrystallization step in which an amorphous semiconductor layer iscrystallized to form a crystalline semiconductor layer. Examples of theelement that promotes crystallization include one or more of iron (Fe),nickel (Ni), cobalt (Co), ruthenium (Ru), rhodium (Rh), palladium (Pd),osmium (Os), iridium (Ir), platinum (Pt), copper (Cu), and gold (Au).

Any method can be used to add a metal element into the amorphoussemiconductor film as long as the method is capable of making the metalelement exist on the surface or at the inside of the amorphoussemiconductor film. For example, a sputtering method, a CVD method, aplasma treatment (including a plasma CVD method), an adsorption method,or a method of applying a metal salt solution can be employed. Amongthem, the method using a solution is simple and easy, and advantageousin easy adjustment of the concentration of the metal element. It ispreferable to form an oxide film on the surface of the amorphoussemiconductor film by UV irradiation in an oxygen atmosphere, a thermaloxidation method, treatment with ozone water or hydrogen peroxideincluding a hydroxyl radical, or the like so that the wettability of thesurface of the amorphous semiconductor film is improved and an aqueoussolution is easily spread over the entire surface of the amorphoussemiconductor film.

In order to remove or reduce the element that promotes crystallizationfrom the crystalline semiconductor layer, a semiconductor layercontaining an impurity element is formed so as to be in contact with thecrystalline semiconductor layer. Such a semiconductor layer containingan impurity element functions as a gettering sink. As the impurityelement, an impurity element imparting n-type conductivity, an impurityelement imparting p-type conductivity, a rare gas element, or the likecan be used. For example, one or more of phosphorus (P), nitrogen (N),arsenic (As), antimony (Sb), bismuth (Bi), boron (B), helium (He), neon(Ne), argon (Ar), krypton (Kr), and xenon (Xe) can be used. Asemiconductor layer containing a rare gas element is formed over thecrystalline semiconductor layer containing the element that promotescrystallization, and thermal treatment (at 550 to 750° C. for 3 minutesto 24 hours) is performed. The element that promotes crystallization inthe crystalline semiconductor layer moves into the semiconductor layercontaining a rare gas element; thus, the element that promotescrystallization in the crystalline semiconductor layer is removed orreduced. After that, the semiconductor layer containing a rare gaselement, which serves as a gettering sink, is removed.

Laser irradiation can be performed by relatively moving a laser beam andthe semiconductor film. For laser irradiation, a marker can be formed inorder to overlap a beam with the semiconductor film with high accuracyor control the start position or the end position of laser irradiation.Such a marker may be formed over the substrate at the same time as theformation of the amorphous semiconductor film.

In the case of using laser irradiation, a continuous-wave laser beam (aCW laser beam) or a pulsed laser beam can be used. Laser beams that canbe used here are beams emitted from one or more kinds of the followinglasers: a gas laser such as an Ar laser, a Kr laser, or an excimerlaser; a laser using, as a medium, single-crystalline YAG, YVO₄,forsterite (Mg₂SiO₄), YAlO₃, or GdVO₄, or polycrystalline (ceramic) YAG,Y₂O₃, YVO₄, YAlO₃, or GdVO₄, to which one or more of Nd, Yb, Cr, Ti, Ho,Er, Tm, and Ta is added as a dopant; a glass laser; a ruby laser; analexandrite laser; a Ti:sapphire laser; a copper vapor laser; and a goldvapor laser. Crystals having a large grain diameter can be obtained byirradiation with the fundamental wave of the above laser beam or thesecond harmonic to the fourth harmonic of the fundamental wave thereof.For example, the second harmonic (532 nm) or the third harmonic (355 nm)of a Nd:YVO₄ laser (the fundamental wave: 1064 nm) can be used. Thislaser can emit either a CW laser beam or a pulsed laser beam. In thecase where a CW laser beam is emitted, the power density of the laserneeds to be about 0.01 to 100 MW/cm² (preferably, 0.1 to 10 MW/cm²). Thescanning rate is set to about 10 to 2000 cm/sec for irradiation.

Note that the laser using, as a medium, single-crystalline YAG, YVO₄,forsterite (Mg₂SiO₄), YAlO₃, or GdVO₄, or polycrystalline (ceramic) YAG,Y₂O₃, YVO₄, YAlO₃, or GdVO₄, to which one or more of Nd, Yb, Cr, Ti, Ho,Er, Tm, and Ta is added as a dopant; an Ar ion laser; or a Ti:sapphirelaser can perform continuous oscillation. In addition, it can alsoperform pulsed oscillation at a repetition rate of greater than or equalto 10 MHz by performing Q-switching operation, mode locking, or thelike. When a laser beam is oscillated at a repetition rate of greaterthan or equal to 10 MHz, it is possible for a semiconductor film to beirradiated with the next pulse after it is melted by the laser beam andbefore it becomes solidified. Therefore, unlike the case of using apulsed laser with a low repetition rate, a solid-liquid interface of thesemiconductor film can be moved continuously. Thus, crystal grains thathave grown continuously in the scanning direction can be obtained.

When ceramic (polycrystal) is used as a medium, the medium can be formedinto a desired shape in a short time at low cost. In the case of usingsingle crystals, a columnar medium having a diameter of severalmillimeters and a length of several tens of millimeters is generallyused. However, in the case of using ceramic, a medium larger than thatcan be formed.

The concentration of the dopant such as Nd or Yb in the medium, whichdirectly contributes to light emission, cannot be changed to a largedegree either in single crystals or polycrystals. Therefore, there is alimitation on improvement of the laser output by increasing theconcentration of the dopant. However, in the case of using ceramic, alaser output can be drastically increased because the size of the mediumcan be significantly increased compared with the case of using singlecrystals.

Further, in the case of using ceramic, a medium with a parallelepipedshape or a rectangular parallelepiped shape can be formed easily. When amedium with such a shape is used and oscillated light is made to travelinside the medium in a zigzag manner, a long oscillation path can beobtained. Therefore, large amplification can be achieved and high outputcan be obtained. In addition, since a laser beam emitted from the mediumwith such a shape has a quadrangular cross section at the time ofemission, it can easily be shaped into a linear beam compared with thecase of using a circular beam, which is advantageous. When the laserbeam emitted in this manner is shaped with an optic system, a linearbeam with a short side of less than or equal to one millimeter and along side of several millimeters to several meters can be easilyobtained. In addition, when the medium is uniformly irradiated withexcitation light, a linear beam with a uniform energy distribution inthe long-side direction can be obtained. Moreover, the semiconductorfilm is preferably irradiated with the laser beam at an incident angleθ(0<θ<90°) in order to prevent laser interference.

When the semiconductor film is irradiated with the linear beam, theentire surface of the semiconductor film can be annealed more uniformly.In the case where uniform annealing is required from one end to theother end of the linear laser beam, it is necessary to exerciseingenuity, for example, by providing slits or the like at both ends soas to shield light at a portion where energy is attenuated.

When the thus obtained linear beam with uniform intensity is used toanneal the semiconductor film and this semiconductor film is used tomanufacture a liquid crystal display device, the liquid crystal displaydevice has favorable and uniform characteristics.

The laser beam irradiation may be performed in an inert gas atmospheresuch as a rare gas or nitrogen. Accordingly, roughness of thesemiconductor surface due to laser beam irradiation can be suppressed,and variation in threshold voltage caused by variation in the interfacestate density can be suppressed.

The amorphous semiconductor film may be crystallized by a combination ofthermal treatment and laser light irradiation, or either thermaltreatment or laser irradiation may be performed a plurality of times.

The gate electrode layer can be formed by a sputtering method, anevaporation method, a CVD method, or the like. The gate electrode layermay be formed using an element selected from tantalum (Ta), tungsten(W), titanium (Ti), molybdenum (Mo), aluminum (Al), copper (Cu),chromium (Cr), and neodymium (Nd), or an alloy material or compoundmaterial containing the element as its main component. Alternatively,the gate electrode layer may be formed using a semiconductor filmtypified by a polycrystalline silicon film doped with an impurityelement such as phosphorus, or an AgPdCu alloy. The gate electrode layermay be a single layer or stacked layers.

In this embodiment mode, the gate electrode layer is formed to have atapered shape; however, the present invention is not limited thereto.The gate electrode layer has a stacked-layer structure, and such astructure may be employed that one layer has a tapered shape and theother layer has a perpendicular side surface formed by anisotropicetching. The gate electrode layers to be stacked may have differenttaper angles or the same taper angle. If the gate electrode layer has atapered shape, the coverage thereof with a film to be stacked thereoveris improved and defects can be reduced to improve reliability.

The source electrode layer or the drain electrode layer can be formed byforming a conductive film by a sputtering method, a PVD method, a CVDmethod, an evaporation method, or the like and then etching theconductive film into a desired shape. Alternatively, the conductivelayer can be formed as selected in a desired position by a dropletdischarge method, a printing method, a dispenser method, anelectroplating method, or the like. Still alternatively, a reflow methodor a damascene method may be used. The source electrode layer or thedrain electrode layer can be formed using a conductive material such asa metal, concretely, a material such as Ag, Au, Cu, Ni, Pt, Pd, Ir, Rh,W, Al, Ta, Mo, Cd, Zn, Fe, Ti, Zr, Ba, Si, or Ge, or an alloy or nitridethereof. Further, a stacked structure thereof may be employed.

The insulating layers 523 and 557 may be formed using an inorganicinsulating material such as silicon oxide, silicon nitride, siliconoxynitride, aluminum oxide, aluminum nitride, or aluminum oxynitride; anacrylic acid, a methacrylic acid, or a derivative thereof; a heatresistant high molecular compound such as polyimide, aromatic polyamide,or polybenzimidazole; or a siloxane resin. Alternatively, a resinmaterial such as a vinyl resin like polyvinyl alcohol orpolyvinylbutyral, an epoxy resin, a phenol resin, a novolac resin, anacrylic resin, a melamine resin, or a urethane resin may be used.Further, an organic material such as benzocyclobutene, fluorinatedarylene ether, or polyimide, a composition material containing awater-soluble homopolymer and a water-soluble copolymer, or the like maybe used. The insulating layers 523, 557 and 527 can be formed by avapor-phase growth method such as a plasma CVD method or a thermal CVDmethod, or a sputtering method. Alternatively, they can be formed by adroplet discharge method or a printing method (such as screen printingor offset printing by which a pattern is formed). A film obtained by acoating method, an SOG film, or the like can also be used.

Without limitation to this embodiment mode, the thin film transistor mayhave a single-gate structure in which a single channel formation regionis formed, a double-gate structure in which two channel formationregions are formed, or a triple-gate structure in which three channelformation regions are formed. In addition, a thin film transistor in aperipheral driver circuit region may also have a single-gate structure,a double-gate structure, or a triple-gate structure.

Note that without limitation to the manufacturing method of a thin filmtransistor described in this embodiment mode, the present invention canbe used in a top-gate structure (such as a staggered structure or acoplanar structure), a bottom-gate structure (such as an invertedcoplanar structure), a dual-gate structure including two gate electrodelayers provided above and below a channel region each with a gateinsulating film interposed therebetween, or other structures.

The transistor may have any structure, as long as the transistor canserve as a switching element. The semiconductor layer may be formedusing various semiconductors such as an amorphous semiconductor, acrystalline semiconductor, a polycrystalline semiconductor, and amicrocrystalline semiconductor, or an organic transistor may be formedusing an organic compound.

Accordingly, in the liquid crystal display device of this embodimentmode using the present invention, deterioration of the liquid crystalwhich is caused in the manufacturing process can be prevented and theliquid crystal display device can have good adhesion between substrates,high reliability and high image quality. Further, such a liquid crystaldisplay device with high reliability and high image quality can bemanufactured with high productivity.

This embodiment mode can be freely combined with Embodiment Mode 1.

Embodiment Mode 4

In this embodiment mode, an example of a liquid crystal display devicein which deterioration of liquid crystal caused in a manufacturingprocess is prevented and which has good adhesion between substrates,higher reliability and high image quality, and, and the manufacturingmethod thereof will be described. Specifically, in this embodiment mode,a liquid crystal display device using a thin film transistor having acrystalline semiconductor film according to the present invention willbe described.

FIG. 12A is a top view illustrating a structure of a display panelaccording to the present invention. A pixel portion 2701 in which pixels2702 are arranged in matrix, a scan line input terminal 2703, and asignal line input terminal 2704 are formed over a substrate 2700 havingan insulating surface. The number of pixels may be determined inaccordance with various standards. In a case of XGA full-color displayusing RGB, the number of pixels may be 1024×768×3 (RGB). In a case ofUXGA full-color display using RGB, the number of pixels may be1600×1200×3 (RGB), and in a case of full-spec, high-definition, andfull-color display using RGB, the number of pixels may be 1920×1080×3(RGB).

The pixels 2702 are formed in matrix by intersections of scan linesextended from the scan line input terminal 2703 and signal linesextended from the signal line input terminal 2704. Each pixel in thepixel portion 2701 is provided with a switching element and a pixelelectrode layer connected thereto. A typical example of the switchingelement is a TFT. A gate electrode layer of the TFT is connected to thescan line, and a source or a drain of the TFT is connected to the signalline, which enables each pixel to be independently controlled by asignal inputted from the outside.

FIG. 12A illustrates a structure of a display panel in which a signal tobe inputted to the scan line and the signal line is controlled by anexternal driver circuit.

Alternatively, a driver IC 2751 may be mounted on the substrate 2700 bya COG (Chip on Glass) method as illustrated in FIG. 13A. As anothermounting mode, a TAB (Tape Automated Bonding) method may be used asillustrated in FIG. 13B. The driver IC may be formed over a singlecrystalline semiconductor substrate or may be formed using a TFT over aglass substrate. In each of FIGS. 13A and 13B, the driver IC 2751 isconnected to an FPC (Flexible Printed Circuit) 2750.

When a TFT provided in a pixel is formed of a crystalline semiconductor,a scanning line driver circuit 3702 can be formed over a substrate 3700as illustrated in FIG. 12B. In FIG. 12B, a pixel portion 3701 iscontrolled by an external driver circuit connected to a signal lineinput terminal 3704, similarly to FIG. 12A. When the TFT provided in apixel is formed of a polycrystalline (microcrystalline) semiconductor, asingle crystalline semiconductor, or the like having high mobility, apixel portion 4701, a scanning line driver circuit 4702, and asignal-line driver circuit 4704 can all be formed over a substrate 4700as illustrated in FIG. 12C.

FIG. 8A is a top view of a liquid crystal display device in thisembodiment mode using the present invention. FIG. 8B is a crosssectional view taken along a line C-D in FIG. 8A.

As illustrated in FIGS. 8A and 8B, a pixel region 606, a driving circuitregion 608 a which is a scanning line driving circuit, and a drivingcircuit region 608 b which is a scanning line driving region are sealedwith a sealant 692 between an element substrate 600 and a countersubstrate 695. A driving circuit region 607 which is a signal linedriving circuit formed with an IC driver is provided over the substrate600.

A transistor 622 and a capacitor 623 are provided in the pixel region606. A driving circuit having transistors 620 and 621 is provided in thedriving circuit region 608 b.

The substrate 600 and the counter substrate 695 are insulatingsubstrates with a light-transmitting property (hereinafter, alsoreferred to as a light-transmitting substrate). The substrateparticularly transmits light in a wavelength region of visible light.For example, a glass substrate such as a barium borosilicate glass oraluminoborosilicate glass, a quartz substrate, or the like can be used.Alternatively, a substrate formed from plastics typified by polyethyleneterephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone(PES), and polycarbonate (PC); or a substrate formed from a flexiblesynthetic resin such as acrylic can be employed. Further alternatively,a film (formed from polypropylene, polyester, vinyl, polyvinyl fluoride,or vinyl chloride), a base film (formed from polyester, polyamide, or aninorganic evaporated film), and the like may be used. Although there isa concern that a substrate formed from a synthetic resin generally has alow heat-resistance temperature compared to another substrate, thesubstrate formed from a synthetic resin can be used when a manufacturingprocess is carried out with a substrate with high heat resistance andthen the substrate with high heat resistance is replaced with thesubstrate formed from a synthetic resin.

In the pixel region 606, a transistor 622 serving as a switching elementis provided, with base films 604 a and 604 b interposed therebetween.

The base films 604 a and 604 b may be formed using a material of anacrylic acid, a methacrylic acid, or derivatives thereof; aheat-resistant high-molecular compound such as polyimide, aromaticpolyamide, or polybenzimidazole; or a siloxane resin. Alternatively, aresin material such as a vinyl resin like polyvinyl alcohol orpolyvinylbutyral, an epoxy resin, a phenol resin, a novolac resin, anacrylic resin, a melamine resin, or a urethane resin may be used.Further, an organic material such as benzocyclobutene, parylene,fluorinated arylene ether, or polyimide, a composition materialcontaining a water-soluble homopolymer and a water-soluble copolymer, orthe like may be used. Moreover, an oxazole resin can be used, and forexample, a photo-curing polybenzoxazole or the like can be used.

The base films 604 a and 604 b can be formed by a sputtering method, aPVD (physical vapor deposition) method, a CVD (chemical vapordeposition) method such as a low-pressure CVD (LPCVD) method or a plasmaCVD method, or the like. Further, a droplet discharge method, a printingmethod (a method for forming a pattern such as screen printing or offsetprinting), a coating method such as a spin coating method, a dippingmethod, a dispenser method, or the like can also be used.

In this embodiment mode, the transistor 622 is a multi-gate thin filmtransistor (TFT), which includes a semiconductor layer includingimpurity regions that function as a source region and a drain region, agate insulating layer, a gate electrode layer having a stacked structureof two layers, and a source electrode layer and a drain electrode layer.The source electrode layer or the drain electrode layer is in contactwith and electrically connects the impurity region of the semiconductorlayer and a pixel electrode layer 630. A thin film transistor can bemanufactured by many methods. For example, a crystalline semiconductorfilm is employed as an active layer. A gate electrode is provided over acrystalline semiconductor film with a gate insulating film interposedtherebetween. An impurity element can be added to the active layer usingthe gate electrode. By addition of an impurity element using the gateelectrode in this manner, a mask does not need to be formed for additionof an impurity element. The gate electrode can have a single-layerstructure or a stacked structure. The impurity region can be formed intoa high-concentration impurity region and a low-concentration impurityregion by controlling the concentration thereof A thin film transistorhaving a low-concentration impurity region in this manner is referred toas an LDD (lightly doped drain) structure. The low-concentrationimpurity region can be formed so as to overlap with the gate electrode,and such a thin film transistor is referred to as a GOLD (gateoverlapped LDD) structure. The polarity of the thin film transistor ismade to be n-type through addition of phosphorus (P) or the like to animpurity region thereof. In a case where a p-type thin film transistoris formed, boron (B) or the like may be added. After that, an insulatingfilm 611 and an insulating film 612 are formed to cover the gateelectrode and the like. Dangling bonds of the crystalline semiconductorfilm can be terminated by a hydrogen element mixed in the insulatingfilm 611 (and the insulating film 612).

In order to further improve planarity, an insulating film 615 and aninsulating film 616 may be formed as interlayer insulating films. Theinsulating films 615 and 616 can be formed using an organic material, aninorganic material, or a stacked structure thereof. For example, theinsulating films 615 and 616 can be formed of a material selected fromsubstances including an inorganic insulating material such as siliconoxide, silicon nitride, silicon oxynitride, silicon nitride oxide,aluminum nitride, aluminum oxynitride, aluminum nitride oxide having ahigher content of nitrogen than that of oxygen, aluminum oxide,diamond-like carbon (DLC), polysilazane, a nitrogen-containing carbon(CN), PSG (phosphosilicate glass), BPSG (borophosphosilicate glass), andalumina. Alternatively, an organic insulating material may be used; anorganic insulating material may be either photosensitive ornon-photosensitive; and polyimide, acrylic, polyamide, polyimide amide,a resist, benzocyclobutene, a siloxane resin, or the like can be used.Note that the siloxane resin corresponds to a resin having Si—O—Sibonds. Siloxane has a skeleton structure formed from a bond of silicon(Si) and oxygen (O). As a substituent, an organic group containing atleast hydrogen (for example, an alkyl group or an aryl group) is used. Afluoro group may be used as the substituent. Alternatively, an organicgroup containing at least hydrogen and a fluoro group may be used as thesubstituent.

The pixel region and the driver circuit region can be formed over thesame substrate with the use of a crystalline semiconductor film. In thatcase, the transistor in the pixel region and the transistor in thedriver circuit region 608 b are formed simultaneously. The transistorused in the driver circuit region 608 b constitutes a part of a CMOScircuit. Although the thin film transistor included in the CMOS circuithas a GOLD structure, it may have an LDD structure like the transistor622.

Without limitation to this embodiment mode, the thin film transistor ofthe pixel region may have a single-gate structure in which a singlechannel formation region is formed, a double-gate structure in which twochannel formation regions are formed, or a triple-gate structure inwhich three channel formation regions are formed. In addition, the thinfilm transistor of a peripheral driver circuit region may also have asingle-gate structure, a double-gate structure, or a triple-gatestructure.

Note that without limitation to the manufacturing method of a thin filmtransistor described in this embodiment mode, the present invention canbe used in a top-gate structure (such as a staggered structure), abottom-gate structure (such as an inversely staggered structure), adual-gate structure including two gate electrode layers provided aboveand below a channel region each with a gate insulating film interposedtherebetween, or another structure.

Next, an insulating layer 631 serving as an alignment film is formed bya printing method or a droplet discharging method to cover the pixelelectrode layer 630 and the insulating film 616. Note that theinsulating layer 631 can be formed as selected by a screen printingmethod or an offset printing method. After that, rubbing treatment isperformed. An insulating layer 633 serving as an alignment film issimilar to the insulating layer 631 serving as an alignment film. Then,the sealant 692 is formed by a droplet discharging method in aperipheral region of the pixel region.

The insulating layer serving as an alignment film can be formed usingpolyimide, polyamide, or the like. The insulating layer can serve as thealignment film by being subjected to rubbing treatment, but it is notlimited as long as the insulating layer can serve as an alignment filmwhich aligns liquid crystal molecules in one direction. Lightirradiation or heat treatment may be performed on the insulating layerto form an alignment film.

The liquid crystal may be dropped to the element substrate 600. Thesealant 692 is provided for the counter substrate 695 provided with acolored layer 635 serving as a color filter and the liquid crystal maybe dropped. Accordingly, the sealant may be provided for either theelement substrate 600 or the counter substrate 695 and the liquidcrystal may be dropped to either the element substrate 600 or thecounter substrate 695. In this embodiment mode, the sealant is providedfor the counter substrate 695 provided with the insulating layer 633serving as an alignment film, a counter electrode layer 634 and thecolored layer 635 serving as a color filter, a first cure treatment isperformed to a surface of the sealant and the liquid crystal is dropped.

In this embodiment mode, a plurality of projections 645 are providedover the substrate 600 which is not provided with the sealant.

Similarly to Embodiment Mode 1, in this embodiment mode using thepresent invention, a surface of an uncured sealant formed over thesubstrate 695 is cured by the first cure treatment before droppingliquid crystal in a method for manufacturing a liquid crystal displaydevice in which the liquid crystal is dropped by a dropping method toform the liquid crystal layer 632. After dropping the liquid crystal,the substrate 695 and the substrate 600 are attached to each other withthe liquid crystal and a space 637 interposed therebetween. Then, thesealant 692 is subjected to a second cure treatment to be cured wholly.In this embodiment mode, the substrate 600 has a plurality ofprojections 645 in an adhesive region of the sealant 692. The substrate600 and the substrate 695 are attached to each other with the liquidcrystal layer 632 interposed therebetween so that the plurality ofprojections 645 is implanted in the sealant formed over the substrate695.

Since a surface of the sealant is cured by the first cure treatment, theliquid crystal is not in contact with the uncured sealant. Accordingly,contamination of the liquid crystal due to the uncured sealant can beprevented. Therefore, reduction in reliability of the liquid crystaldisplay device caused by deterioration of the liquid crystal can beprevented. The liquid crystal display device with reduced displayunevenness, a reduced display defect and high image quality can berealized.

In this embodiment mode, although the surface of the sealant is cured bythe first cure treatment, an inside of the sealant is still in anuncured state in which adhesiveness is high. Since an adhesive region ofthe sealant 692 formed over the substrate 600 is provided with theplurality of projections 645, when the substrate 695 and the substrate600 are attached to each other, the plurality of projections 645 isimplanted in the sealant. The projections 645 physically destroy thesurface of the sealant of which adhesiveness is lowered by curetreatment and penetrate the inside of the sealant, so that theprojections can be in contact with the uncured sealant with highadhesiveness. Accordingly, the second cure treatment is performed in astate where the plurality of projections 645 is implanted in the sealantand the sealant 692 is wholly cured, whereby the substrate 695 and thesubstrate 600 can be attached firmly to each other and can stick to eachother. Adhesiveness between the substrate 695 and the substrate 600 canbe improved and reliability of the liquid crystal display device can beimproved.

In this embodiment mode, cure treatment is performed at least twice ormore; the first cure treatment is treatment in which only the surface ofthe sealant is cured and the second cure treatment is treatment in whichthe sealant is wholly cured in a state where the projections 645 areimplanted in the sealant. Each of the first cure treatment and thesecond cure treatment may be performed once or a plurality of times. Thesame treatment may be performed (for example, light irradiationtreatment is performed twice) or the different treatments may beperformed (for example, the first is light irradiation treatment and thesecond is heat treatment) as the cure treatments.

As the cure treatment, light irradiation treatment using ultravioletrays, or the like or heat treatment may be performed. When anultraviolet curing resin is used as the sealant, the ultraviolet curingresin is cured by an ultraviolet irradiation treatment. When athermosetting resin is used, heat treatment may be performed. Inaddition, heat treatment may be performed to the ultraviolet curingresin. Light for light irradiation may be light emitted from a lamp orlaser light. A method and conditions (energy, time, pressure,atmosphere, and the like) of an irradiation treatment may be set asappropriate in accordance with a material used for the sealant. Further,a method and conditions (temperature, time, pressure, atmosphere, andthe like) of heat treatment may also be set as appropriate in accordancewith a property of the sealant.

The projections 645 physically destroy the cured region which is asurface of the sealant. It is acceptable as long as the projections 645have strength and height with which the projections can reach theuncured region inside the sealant, and there is no particular limitationon a material and a shape used for the projections. The projections 645preferably have shapes with a function as a wedge so that theprojections are easily implanted in the sealant and adhesion between theprojections and the sealant is improved. A pyramid shape such as apointed needle-like shape (e.g. a cone shape and a polygonal pyramid), atriangular pole of which side surface is provided so as to be in contactwith the substrate, or the like can be used.

The projections 645 may be formed using the same material as a componentof the liquid crystal display device and in the same process as theliquid crystal display device. Further, only the projections 645 may beformed in a different process. In this embodiment mode, the plurality ofprojections 645 with a needle-like shape are provided over theinsulating film 612.

Further, asperity may be formed so that the function of the projectionas a wedge can be improved by processing a surface of the projection645. When the projection 645 has an anchor effect of functioning as awedge, the substrate 695 and the substrate 600 can be attached morefirmly. The asperity may be formed by addition of physical force orimpact to the projection 645. The projection 645 may be changedpartially (being dissolved partially, or the like) by a chemicaltreatment (corrosion, or the like of a surface by a solution with acorrosion effect) or heating to form the asperity.

The plurality of projections 645 may be formed by processing thesubstrate or may also be formed over the substrate by formation of afilm, or the like. Alternatively, the projections 645 may be formed in adifferent process and attached to the substrate with an adhesive agent,or the like. As a substrate over which the projections 645 are provided,a glass substrate and a quartz substrate, or the like can be used. Aflexible substrate may also be used. The flexible substrate indicates asubstrate that can be bent.

As the flexible substrate, a high-molecular material elastomer, whichcan be processed to be shaped similarly to plastic by plasticization athigh temperature, and has a property such as an elastic body like rubberat room temperature, or the like can be given in addition to a plasticsubstrate made of polycarbonate, polyarylate, polyethersulfone, or thelike. Alternatively, a film (made of polypropylene, polyester, vinyl,polyvinyl fluoride, vinyl chloride, or the like) or an inorganic vapordeposition film can be used. In this manner, the liquid crystal displaydevice of the present invention can be formed employing various shapeshaving the plurality of projections.

A material for forming the projection 645 may be an inorganic materialor an organic material and may be an insulating material or a conductivematerial. For example, as a material for forming the projection 645,silicon, nitrogen, fluorine, oxide, nitride, fluoride, or the like canbe used. As oxide, the following can be used: silicon oxide, boricoxide, sodium oxide, magnesium oxide, aluminum oxide (alumina),potassium oxide, calcium oxide, diarsenic trioxide (arsenious oxide),strontium oxide, antimony oxide, barium oxide, indium tin oxide (ITO),zinc oxide (ZnO), indium zinc oxide (IZO) in which zinc oxide (ZnO) ismixed in indium oxide, a conductive material in which silicon oxide ismixed in indium oxide, organic indium, organic tin, indium oxidecontaining tungsten oxide, indium zinc oxide containing tungsten oxide,indium oxide containing titanium oxide, indium tin oxide containingtitanium oxide, or the like. As the nitride, aluminum nitride, siliconnitride, or the like can be used. As the fluoride, lithium fluoride,sodium fluoride, magnesium fluoride, calcium fluoride, lanthanumfluoride, or the like can be used. The material used for the projectionsmay include one or more kinds of the above-described silicon, nitrogen,fluorine, oxide, nitride, and fluoride. The above-described materialsused for the substrate can also be used.

As other materials used for the projection 645, a high molecule such aspolyimide, aromatic polyamide, or polybenzimidazole; or a siloxane resinmay be used. Alternatively, a resin material such as a vinyl resin likepolyvinyl alcohol or polyvinylbutyral, an epoxy resin, a phenol resin, anovolac resin, an acrylic resin, a melamine resin, or a urethane resinmay be used. In addition, metal such as Ag, Au, Cu, Ni, Pt, Pd, Ir, Rh,W, or Al, metal sulfide such as Cd or Zn, an oxide of Fe, Ti, Si, Ge,Zr, Ba, or the like, or a mixture of the materials may also be used.

The plurality of projections 645 can be formed in a manner such that athin film is formed by a sputtering method, a vacuum evaporation method,a PVD (physical vapor deposition) method, or a CVD (Chemical VaporDeposition) method such as a low-pressure CVD (LPCVD) method or a plasmaCVD method, and then etched into a desired shape. Alternatively, adroplet discharging method by which a pattern can be formed as selected,a printing method by which a pattern can be transferred or drawn (amethod for forming a pattern such as screen printing or offsetprinting), a coating method, such as a spin coating method, a dippingmethod, a dispenser method, a brush coating method, a spraying method, aflow coating method, or the like can be employed. Still alternatively,an imprinting technique or a nanoimprinting technique with which ananoscale three-dimensional structure can be formed by a transfertechnology can be employed. Imprinting and nanoimprinting are techniquesfor forming a minute three-dimensional structure without using aphotolithography process.

A spacer 637 which controls a distance between the substrate 695 and thesubstrate 600 may be formed in the sealant formation regions of thesubstrate 695 and the substrate 600.

After the substrate 695 and the substrate 600 are attached to each otherwith the filled liquid crystal layer 632 interposed therebetween, thesealant is preferably cured and subjected to heat treatment. By heattreatment, the sealant is further cured, so that the adhesive strengthcan be improved and orientation disorder of the liquid crystal can becorrected. A process of attaching is preferably conducted under areduced pressure.

As the sealant, typically, a visible light curable resin, an ultravioletcurable resin, or a thermosetting resin can be used. For example, anepoxy resin such as a bisphenol-A liquid resin, a bisphenol-A solidresin, a bromine-containing epoxy resin, a bisphenol-F resin, abisphenol-AD resin, a phenol resin, a cresol resin, a novolac resin, acycloaliphatic epoxy resin, an Epi-Bis type epoxy resin, a glycidylester resin, a glycidyl amine resin, a heterocyclic epoxy resin, or amodified epoxy resin can be used. The uncured sealant can be formedusing a droplet discharging method by which a pattern can be formed asselected, a printing method by which a pattern can be transferred ordrawn (a method for forming a pattern, such as screen printing or offsetprinting), a dispenser method, or the like.

Then, a polarizing plate 641 is provided to the outer side of thecounter substrate 695 and a polarizing plate 643 is provided to theopposite side of the substrate 600 from the element. The polarizingplate can be attached to the substrate with use of an adhesive layer. Aretardation plate may be provided between the polarizing plate and thesubstrate. A filler may be mixed into the sealant, and the countersubstrate 695 may be provided with a shielding film (black matrix) orthe like . Note that a color filter or the like may be formed ofmaterials which exhibit red (R), green (G), and blue (B) in the casewhere the liquid crystal display device is a full-color display; and thecolored layer may be omitted or may be formed of a material whichexhibits at least one color in the case where the liquid crystal displaydevice is a single-color display.

Note that the color filter is not always provided in the case wherelight-emitting diodes (LEDs) of RGB or the like are arranged in abacklight unit and a successive additive color mixing method (fieldsequential method) in which color display is performed by time divisionis employed. The black matrix is preferably provided so as to overlapwith a transistor and a CMOS circuit for the sake of reducing reflectionof external light by wirings of the transistor and the CMOS circuit.Note that the black matrix may be provided so as to overlap with acapacitor. This is because reflection by a metal film included in thecapacitor can be prevented.

While the spacer may be provided in such a way that particles having asize of several micrometers are sprayed, the spacer in this embodimentmode is formed by a method in which a resin film is formed over theentire surface of the substrate and then etched. A material of thespacer is applied by a spinner and then subjected to light exposure anddevelopment to form a predetermined pattern. In addition, the materialis heated at 150° C. to 200° C. in a clean oven or the like so as to behardened. The thus manufactured spacer can have various shapes dependingon the conditions of the light exposure and development It is preferablethat the spacer have a columnar shape with a flat top so that mechanicalstrength of the liquid crystal display device can be secured when thecounter substrate is attached. The shape of the spacer can be conical,pyramidal, or the like, and there is no particular limitation thereon.The spacer may be provided in the sealant formation regions (sealantadhesive regions) of the first substrate (the substrate 695) and thesecond substrate (the substrate 600).

Then, a terminal electrode layer 678 electrically connected to the pixelregion is attached to an FPC 694 which is a wiring board for connection,through an anisotropic conductive layer 696. The FPC 694 transmitsexternal signals or potential. Through the foregoing steps, a liquidcrystal display device having a display function can be manufactured.

A wiring and a gate electrode layer which are included in a transistor,the pixel electrode layer 630, and the counter electrode layer 634 areformed using one or a plurality of the following; indium tin oxide(ITO), indium zinc oxide (IZO) in which zinc oxide (ZnO) is mixed intoindium oxide, a conductive material in which silicon oxide (SiO₂) ismixed into indium oxide, organic indium, organic tin, indium oxidecontaining tungsten oxide, indium zinc oxide containing tungsten oxide,indium oxide containing titanium oxide, or indium tin oxide containingtitanium oxide; or metal such as tungsten (W), molybdenum (Mo),zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta),chromium (Cr), cobalt (Co), nickel (Ni), titanium (Ti), platinum (Pt),aluminium (Al), copper (Cu), or silver (Ag), or alloy or nitride of anyof those metals.

In the case of a transmissive liquid crystal display device, a lighttransmitting conductive material may be used for the pixel electrodelayer 630 and the counter electrode layer 634. In the case of areflective liquid crystal display device, a reflective layer may beadditionally provided. Alternatively, a reflective conductive materialis used for the pixel electrode layer 630 and a light transmittingconductive material is used for the counter electrode layer 634 so thatlight reflected by the pixel electrode layer 630 passes through thecounter electrode layer 634 and is emitted from the viewing side.

The source electrode layer or the drain electrode layer may be connectedto the pixel electrode layer through a wiring layer so as to beelectrically connected instead of being directly in contact with eachother. Alternatively, the pixel electrode layer may be partially stackedover the source electrode layer or the drain electrode layer.

Further alternatively, the pixel electrode layer may be formed first andthen the source electrode layer or the drain electrode layer may beformed to be in contact with the pixel electrode layer.

While the foregoing circuits are used in this embodiment mode, thepresent invention is not limited thereto and an IC chip may be mountedas a peripheral driver circuit by a COG method or a TAB method which aredescribed above. Further, a gate line driver circuit and a source linedriver circuit may be provided or pluralities of the gate line drivercircuits and source line driver circuits may be provided.

In the liquid crystal display device of the present invention, there isno particular limitation on a driving method for image display, and forexample, a dot sequential driving method, a line sequential drivingmethod, an area sequential driving method, or the like may be used.Typically, the line sequential driving method is used, and a timedivision gray scale driving method or an area gray scale driving methodmay be used as appropriate. Further, an image signal inputted to thesource line of the liquid crystal display device may be either an analogsignal or a digital signal. The driver circuit and the like may bedesigned as appropriate depending on the image signal.

Accordingly, in the liquid crystal display device of this embodimentmode using the present invention, deterioration of the liquid crystalwhich is caused in the manufacturing process can be prevented and theliquid crystal display device can have good adhesion between substrates,high reliability and high image quality. Further, such a liquid crystaldisplay device with high reliability and high image quality can bemanufactured with high productivity.

This embodiment mode can be freely combined with Embodiment Mode 1.

Embodiment Mode 5

In this embodiment mode, an example of a liquid crystal display devicein which deterioration of liquid crystal caused in a manufacturingprocess is prevented and which has higher reliability, higher imagequality, and good adhesion between substrates, and the manufacturingmethod thereof will be described. Specifically, in this embodiment mode,a liquid crystal display device according to the present invention usinga thin film transistor having an amorphous semiconductor film will bedescribed.

A liquid crystal display device illustrated in FIG. 9 includes, over anelement substrate 200, a transistor 220 which is an inversely staggeredthin film transistor, a pixel electrode layer 201, an insulating film202, an insulating layer 203 serving as an alignment film, a liquidcrystal layer 204, a spacer 281, an insulating layer 205 serving as analignment film, a counter electrode layer 206, a color filter 208, ablack matrix 207, a counter substrate 210, and polarizing plates 231 and233 in a pixel region; and includes a sealant 282, a terminal electrodelayer 287, an anisotropic conductive layer 285, and an FPC 286 in asealing region.

The insulating layer serving as an alignment film can be formed usingpolyimide, polyamide, or the like. The insulating layer can serve as thealignment film by being subjected to rubbing treatment, but it is notlimited as long as the insulating layer can serve as an alignment filmwhich aligns liquid crystal molecules in one direction. Lightirradiation or heat treatment may be performed on the insulating layerto form an alignment film.

The liquid crystal may be dropped to the element substrate 200. Thesealant 282 is formed over the counter substrate 210 and the liquidcrystal may be dropped. Accordingly, the sealant may be provided foreither the element substrate 200 or the counter substrate 210 and theliquid crystal may be dropped to either the element substrate 200 or thecounter substrate 210. In this embodiment mode, the sealant is providedfor the counter substrate 210, a first cure treatment is performed to asurface of the sealant and the liquid crystal is dropped. In thisembodiment mode, a plurality of projections 235 are provided over thesubstrate 200 which is not provided with the sealant. The projections235 are formed so as to avoid a formation region of a wiring layer whichis connected to the terminal electrode layer 287.

Similarly to Embodiment Mode 1, in this embodiment mode using thepresent invention, a surface of an uncured sealant formed over thesubstrate 210 is cured by the first cure treatment before droppingliquid crystal in a method for manufacturing a liquid crystal displaydevice in which the liquid crystal is dropped by a dropping method toform the liquid crystal layer 204. After dropping the liquid crystal,the substrate 210 and the substrate 200 are attached to each other withthe liquid crystal and the spacer 281 interposed therebetween. Then, thesealant 282 is subjected to a second cure treatment to be cured wholly.In this embodiment mode, the substrate 200 has a plurality ofprojections 235 in an adhesive region of the sealant 282. The substrate200 and the substrate 210 are attached to each other with the liquidcrystal interposed therebetween so that the plurality of projections 235is implanted in the sealant formed over the substrate 210.

Since a surface of the sealant is cured by the first cure treatment, theliquid crystal is not in contact with the uncured sealant. Accordingly,contamination of the liquid crystal due to the uncured sealant can beprevented. Therefore, reduction in reliability of the liquid crystaldisplay device caused by deterioration of the liquid crystal can beprevented. The liquid crystal display device with reduced displayunevenness, a reduced display defect and high image quality can berealized.

In this embodiment mode, although the surface of the sealant is cured bythe first cure treatment, an inside of the sealant is still in anuncured state in which adhesiveness is high. Since an adhesive region ofthe sealant 282 of the substrate 200 is provided with the plurality ofprojections 235, when the substrate 210 and the substrate 200 areattached to each other, the plurality of projections 235 is implanted inthe sealant. The projections 235 physically destroy the surface of thesealant of which adhesiveness is lowered by cure treatment and penetratethe inside of the sealant, so that the projections can be in contactwith the uncured sealant with high adhesiveness, Accordingly, the secondcure treatment is performed in a state where the plurality ofprojections 235 is implanted in the sealant and the sealant 282 iswholly cured, whereby the substrate 210 and the substrate 200 can beattached firmly to each other and can stick to each other. Adhesivenessbetween the substrate 210 and the substrate 200 can be improved andreliability of the liquid crystal display device can be improved.

In this embodiment mode, cure treatment is performed at least twice ormore; the first cure treatment is treatment in which only the surface ofthe sealant is cured and the second cure treatment is treatment in whichthe sealant is wholly cured in a state where the projections 235 areimplanted in the sealant. Each of the first cure treatment and thesecond cure treatment may be performed once or a plurality of times. Thesame treatment may be performed (for example, light irradiationtreatment is performed twice) or the different treatments may beperformed (for example, the first is light irradiation treatment and thesecond is heat treatment) as the cure treatments.

As the cure treatment, light irradiation treatment using ultravioletrays, or the like or heat treatment may be performed. When anultraviolet curing resin is used as the sealant, the ultraviolet curingresin is cured by an ultraviolet irradiation treatment. When athermosetting resin is used, heat treatment may be performed. Inaddition, heat treatment may be performed to the ultraviolet curingresin. Light for light irradiation may be light emitted from a lamp orlaser light. A method and conditions (energy, time, pressure,atmosphere, and the like) of an irradiation treatment may be set asappropriate in accordance with a material used for the sealant. Further,a method and conditions (temperature, time, pressure, atmosphere, andthe like) of heat treatment may also be set as appropriate in accordancewith a property of the sealant.

The projections 235 physically destroy the cured region which is asurface of the sealant. It is acceptable as long as the projections 645have strength and height with which the projections can reach theuncured region inside the sealant, and there is no particular limitationon a material and a shape used for the projections. The projections 235preferably have shapes with a function as a wedge so that theprojections are easily implanted in the sealant and adhesion between theprojections and the sealant is improved. A pyramid shape such as apointed needle-like shape (e.g. a cone shape and a polygonal pyramid), atriangular pole of which side surface is provided so as to be in contactwith the substrate, or the like can be used.

The projections 235 may be formed using the same material as a componentof the liquid crystal display device and in the same process as theliquid crystal display device. Further, only the projections 235 may beformed in a different process. In this embodiment mode, the plurality ofprojections 235 with a needle-like shape are provided over the substrate200.

Further, asperity may be formed so that the function of the projectionas a wedge can be improved by processing a surface of the projection235. When the projection 235 has an anchor effect of functioning as awedge, the substrate 210 and the substrate 200 can be attached to eachother more firmly. The asperity may be formed by addition of physicalforce or impact to the projection 235. The projection 235 may be formedby being changed partially (being dissolved partially, or the like) by achemical treatment (corrosion, or the like of a surface by a solutionwith a corrosion effect) or heating to form the asperity.

The plurality of projections 235 may be formed by processing thesubstrate or may also be formed over the substrate by formation of afilm, or the like. Alternatively, the projections 235 may be formed in adifferent process and attached to the substrate with an adhesive agent,or the like. As a substrate over which the projections 235 are provided,a glass substrate, a quartz substrate, or the like can be used. Aflexible substrate may also be used. The flexible substrate indicates asubstrate that can be bent. As the flexible substrate, a high-molecularmaterial elastomer, which can be processed to be shaped similarly toplastic by plasticization at high temperature, and has a property suchas an elastic body like rubber at room temperature, or the like can begiven in addition to a plastic substrate made of polycarbonate,polyarylate, polyethersulfone, or the like. Alternatively, a film (madeof polypropylene, polyester, vinyl, polyvinyl fluoride, vinyl chloride,or the like) or an inorganic vapor deposition film can be used. In thismanner, the liquid crystal display device of the present invention canbe formed employing various shapes having the plurality of projections235.

A material for forming the projection 235 may be an inorganic materialor an organic material and may be an insulating material or a conductivematerial. For example, as a material for forming the projection 235,silicon, nitrogen, fluorine, oxide, nitride, fluoride, or the like canbe used. As oxide, the following can be used: silicon oxide, boricoxide, sodium oxide, magnesium oxide, aluminum oxide (alumina),potassium oxide, calcium oxide, diarsenic trioxide (arsenious oxide),strontium oxide, antimony oxide, barium oxide, indium tin oxide (ITO),zinc oxide (ZnO), indium zinc oxide (IZO) in which zinc oxide (ZnO) ismixed in indium oxide, a conductive material in which silicon oxide ismixed in indium oxide, organic indium, organic tin, indium oxidecontaining tungsten oxide, indium zinc oxide containing tungsten oxide,indium oxide containing titanium oxide, indium tin oxide containingtitanium oxide, or the like. As the nitride, aluminum nitride, siliconnitride, or the like can be used. As the fluoride, lithium fluoride,sodium fluoride, magnesium fluoride, calcium fluoride, lanthanumfluoride, or the like can be used. The material used for the projectionsmay include one or more kinds of the above-described silicon, nitrogen,fluorine, oxide, nitride, and fluoride. The above-described materialsused for the substrate can also be used.

As other materials used for the projection 235, a high molecule such aspolyimide, aromatic polyamide, or polybenzimidazole; or a siloxane resinmay be used. Alternatively, a resin material such as a vinyl resin likepolyvinyl alcohol or polyvinylbutyral, an epoxy resin, a phenol resin, anovolac resin, an acrylic resin, a melamine resin, or a urethane resinmay be used. In addition, metal such as Ag, Au, Cu, Ni, Pt, Pd, Tr, Rh,W, or Al, metal sulfide such as Cd or Zn, an oxide of Fe, Ti, Si, Ge,Zr, Ba, or the like, or a mixture of the materials may also be used.

The plurality of projections 235 can be formed in a manner such that athin film is formed by a sputtering method, a vacuum evaporation method,a PVD (physical vapor deposition) method, or a CVD (Chemical VaporDeposition) method such as a low-pressure CVD (LPCVD) method or a plasmaCVD method, and then etched into a desired shape. Alternatively, adroplet discharging method by which a pattern can be formed as selected,a printing method by which a pattern can be transferred or drawn (amethod for forming a pattern such as screen printing or offsetprinting), a coating method, such as a spin coating method, a dippingmethod, a dispenser method, a brush coating method, a spraying method, aflow coating method, or the like can be employed. Still alternatively,an imprinting technique or a nanoimprinting technique with which ananoscale three-dimensional structure can be formed by a transfertechnology can be employed. Imprinting and nanoimprinting are techniquesfor forming a minute three-dimensional structure without using aphotolithography process.

A spacer 281 which controls a distance between the substrate 210 and thesubstrate 200 may be formed in the sealant formation regions of thesubstrate 210 and the substrate 200.

After the substrate 210 and the substrate 200 are attached to each otherwith the filled liquid crystal layer 204 interposed therebetween, thesealant is preferably cured and subjected to heat treatment. By heattreatment, the sealant is further cured, so that the adhesive strengthcan be improved and orientation disorder of the liquid crystal can becorrected. A process of attaching is preferably conducted under areduced pressure.

As the sealant 282, typically, a visible light curable resin, anultraviolet curable resin, or a thermosetting resin can be used. Forexample, an epoxy resin such as a bisphenol-A liquid resin, abisphenol-A solid resin, a bromine-containing epoxy resin, a bisphenol-Fresin, a bisphenol-AD resin, a phenol resin, a cresol resin, a novolacresin, a cycloaliphatic epoxy resin, an Epi-Bis type epoxy resin, aglycidyl ester resin, a glycidyl amine resin, a heterocyclic epoxyresin, or a modified epoxy resin can be used. The uncured sealant can beformed using a droplet discharging method by which a pattern can beformed as selected, a printing method by which a pattern can betransferred or drawn (a method for forming a pattern, such as screenprinting or offset printing), a dispenser method, or the like.

A gate electrode layer, a source electrode layer, and a drain electrodelayer of the inverted staggered thin film transistor 220 in thisembodiment mode are formed by a droplet discharging method. A dropletdischarging method is a method in which a composition including aconductive material in a liquid state is discharged and then solidifiedby drying and/or baking, whereby a conductive layer or an electrodelayer is formed. When a composition containing an insulating material isdischarged and then solidified by drying and/or baking, an insulatinglayer can also be formed. Because a component of a liquid crystaldisplay device, such as a conductive layer or an insulating layer, canbe formed as selected, steps are simplified and material loss can beprevented. Therefore, a liquid crystal display device can bemanufactured at low cost with high productivity.

In this embodiment mode, an amorphous semiconductor is used as asemiconductor layer, and a semiconductor layer having one conductivitytype may be formed if needed. In this embodiment mode, a semiconductorlayer and an n-type amorphous semiconductor layer which is thesemiconductor layer having one conductivity type are stacked. Further,an n-channel thin film transistor with an NMOS structure which includesan n-type semiconductor layer, a p-channel thin film transistor with aPMOS structure which includes a p-type semiconductor layer, or a CMOSstructure which includes an n-channel thin film transistor and ap-channel thin film transistor can be manufactured. In this embodimentmode, the transistor 220 is an n-channel inverted staggered thin filmtransistor. The transistor 220 can be a channel protective type invertedstaggered thin film transistor in which a protective layer is providedover the channel region of the semiconductor layer.

In addition, an n-channel thin film transistor or a p-channel thin filmtransistor can be formed by doping the semiconductor layer with anelement imparting conductivity and forming an impurity region. Insteadof formation of the n-type semiconductor layer, a plasma treatment maybe performed with a PH₃ gas to impart conductivity to the semiconductorlayer.

The semiconductor layer can be formed with use of an organicsemiconductor material as a semiconductor, by a printing method, a spraymethod, a spin coating method, a droplet discharge method, a dispensermethod, or the like. In this case, since an etching step is not alwaysnecessary, the number of steps can be reduced. As an organicsemiconductor, a low molecular material such as pentacene or a highmolecular material can be used, or a material such as an organic pigmentor a conductive high molecular organic material can be used. As anorganic semiconductor material used in the present invention, an-conjugated high molecular material with its skeleton including aconjugate double bond is desirable. Typically, a soluble high molecularmaterial such as polythiophene, polyfluorene, poly(3-alkylthiophene), ora polythiophene derivative can be used.

The structure of a backlight unit 352 will be described. The backlightunit 352 includes a light source 331 which emits light such as a coldcathode tube, a hot cathode fluorescent lamp, a light-emitting diode, aninorganic EL, or an organic EL, a lamp reflector 332 for effectivelyleading light to a light guiding plate 335, the light guiding plate 335for totally reflecting light so that light is led to the entire surfaceof a liquid crystal display device, a diffusing plate 336 for reducingvariations in brightness, and a reflector plate 334 for reusing lightleaked under the light guiding plate 335.

A control circuit for adjusting luminance of the light source 331 isconnected to the backlight unit 352. The luminance of the light source331 can be controlled by a signal supplied from the control circuit.

Accordingly, in the liquid crystal display device of this embodimentmode using the present invention, deterioration of the liquid crystalwhich is caused in a manufacturing process can be prevented. Further,the liquid crystal display device with good adhesion between substrates,high reliability and high image quality can be realized. Moreover, sucha liquid crystal display device with high reliability and high imagequality can be manufactured with high productivity.

This embodiment mode can be freely combined with Embodiment Mode 1.

Embodiment Mode 6

This embodiment mode describes operation of circuits included in theliquid crystal display device according to the present invention.

FIGS. 14A to 14C illustrate system block diagrams of a pixel portion 705and a driver circuit portion 708 in a liquid crystal display device.

In the pixel portion 705, a plurality of pixels are included. Aswitching element is provided in each intersection region of signallines 712 and scanning lines 710, which serves as a pixel. Applicationof voltage for controlling tilt of liquid crystal molecules can becontrolled by the switching elements. Such a structure in which aswitching element is provided in each intersection region is called anactive matrix type. The pixel portion of the present invention is notlimited to an active matrix type, and may have a passive matrix typestructure instead. The passive matrix type is manufactured by a simpleprocess because a switching element is not included in each pixel.

The driver circuit portion 708 includes a control circuit 702, a signalline driver circuit 703, and a scanning line driver circuit 704. Thecontrol circuit 702 controls a gray scale in accordance with contents tobe displayed by the pixel portion 705.

Therefore, the control circuit 702 inputs a generated signal to thesignal line driver circuit 703 and the scanning line driver circuit 704.When a switching element is selected by the scanning line driver circuit704 using the scanning line 710, voltage is applied to a pixel electrodein a selected intersection region. A value of this voltage is determinedbased on a signal inputted from the signal line driver circuit 703through the signal line.

Further, in the control circuit 702, a signal for controlling electricpower supplied to a lighting unit 706 is generated. The signal isinputted to a power supply 707 of the lighting unit 706. As the lightingunit, the back light unit described in the foregoing embodiment mode canbe used. Note that the lighting unit may be a front light instead of thebacklight unit. A front light is a plate-like lighting unit whichincludes a light emitter and a light guide body for illuminating thewhole liquid crystal display device, and which is attached to a frontsurface side of the pixel portion. With such a lighting unit, the pixelportion can be evenly irradiated with light, with low power consumption.

As illustrated in FIG. 14B, a scanning line driver circuit 704 includescircuits serving as a shift register 741, a level shifter 742, and abuffer 743. Signals such as a gate start pulse (GSP) and a gate clocksignal (GCK) are inputted to the shift register 741. Note that astructure of the scanning line driver circuit of the present inventionis not limited to the structure illustrated in FIG. 14B.

As illustrated in FIG. 14C, the signal line driver circuit 703 includescircuits serving as a shift register 731, a first latch 732, a secondlatch 733, a level shifter 734, and a buffer 735. The circuit serving asthe buffer 735 is a circuit for amplifying a weak signal and includes anoperational amplifier and the like. A signal such as a start pulse(SSP), a clock signal (SCK), and the like are inputted to the shiftregister 731 and data (DATA) such as a video signal are inputted to thefirst latch 732. Latch (LAT) signals can be temporarily held in thesecond latch 733, and they are inputted to the pixel portion 705 at atime. Such operation is referred to as line sequential driving. If thepixels perform dot sequential driving instead of the line sequentialdriving, the second latch is not required. Thus, a structure of a signalline driver circuit of the present invention is not limited to thestructure illustrated in FIG. 14C.

The signal line driver circuit 703, the scanning line driver circuit704, and the pixel portion 705 as described above can be formed ofsemiconductor elements provided over one substrate. The semiconductorelement can be formed by using a thin film transistor formed over aglass substrate. In that case, a crystalline semiconductor film may beapplied to the semiconductor elements (see Embodiment Mode 4). Acrystalline semiconductor film can be included in a circuit in a drivercircuit portion because its electrical characteristics, in particular,the mobility, is high.

Further, the signal line driver circuit 703 and the scanning line drivercircuit 704 can be mounted over the substrate by using an integratedcircuit (IC) chip. In that case, an amorphous semiconductor film can beapplied to a semiconductor element in the pixel portion (see EmbodimentMode 5).

Accordingly, in the liquid crystal display device of this embodimentmode using the present invention, deterioration of the liquid crystalwhich is caused in a manufacturing process can be prevented. Further,the liquid crystal display device with good adhesion between substrates,high reliability and high image quality can be realized. Moreover, sucha liquid crystal display device with high reliability and high imagequality can be manufactured with high productivity.

Embodiment Mode 7

This embodiment mode describes a structure of a backlight, which is alighting unit which can be used in a liquid crystal display deviceaccording to the present invention. A backlight is provided in a liquidcrystal display device as a backlight unit having a light source. In thebacklight unit, the light source is surrounded by a reflector plate sothat light is scattered efficiently.

As illustrated in FIG. 11A, a cold cathode tube 401 can be used as alight source in a backlight unit 352. In order to efficiently reflectlight from the cold cathode tube 401, a lamp reflector 332 can beprovided. The cold cathode tube 401 is mostly used for a large-sizedliquid crystal display device due to high luminance from the coldcathode tube. Accordingly, the backlight unit having a cold cathode tubecan be used for a display of a personal computer.

As illustrated in FIG. 11B, a light-emitting diode 402 can be used as alight source of the backlight unit 352. For example, light-emittingdiodes 402 which emit white light are arranged at predeterminedintervals. In order to efficiently reflect light from the light-emittingdiode 402, the lamp reflector 332 can be provided.

As illustrated in FIG. 11C, light-emitting diodes 403, 404, and 405which emit light of colors of RGB can be used as a light source in thebacklight unit 352. When the light-emitting diodes 403, 404, and 405which emit light of colors of RGB are used, color reproducibility can beenhanced as compared with the case where only the light-emitting diode402 which emits white light is used. In order to efficiently reflectlight from the light emission diodes, the lamp reflector 332 can beprovided.

As illustrated in FIG. 11D, when the light-emitting diodes 403, 404, and405 which emit light of colors of RGB are used as a light source, it isnot necessary that the number and arrangement of the light-emittingdiodes 403, 404, and 405 are the same. For example, a plurality oflight-emitting diodes emitting light of a color that has lowlight-emitting intensity may be arranged.

Further, the light-emitting diode 402 which emits light of a white colorand the light-emitting diodes 403, 404, and 405 which emit light ofcolors of RGB may be combined.

When a field sequential mode is applied in the case of using thelight-emitting diodes of RGB, color display can be performed bysequentially lighting the light-emitting diodes of RGB in accordancewith the time.

The light-emitting diode is suitable for a large-sized liquid crystaldisplay device because the luminance thereof is high. In addition, colorreproducibility of the light-emitting diode is superior to that of acold cathode tube because the color purity of each color of RGB isfavorable, and the area required can be reduced. Therefore, a narrowerframe can be achieved when the light-emitting diode is applied to asmall-sized liquid crystal display device.

A light source does not need to be provided as in the backlight unitsillustrated in FIGS. 11A to 11D. For example, when a backlight having alight-emitting diode is mounted on a large-sized liquid crystal displaydevice, the light-emitting diode can be disposed behind the substrate.In that case, each of the light-emitting diodes can be arranged atpredetermined intervals. Depending on arrangement of the light-emittingdiodes, color reproducibility can be enhanced.

A liquid crystal display device using such a backlight according to thepresent invention can have good adhesion between substrates, highreliability and high image quality and deterioration of liquid crystalcaused in a manufacturing process thereof can be prevented. Further,such a liquid crystal display device with high reliability and highimage quality can be manufactured with high productivity. A backlighthaving a light-emitting diode is particularly suitable for a large-sizedliquid crystal display device, and a high-quality image can be providedeven in a dark place by enhancement of the contrast ratio of thelarge-sized liquid crystal display device.

This embodiment mode can be combined with any of Embodiment Modes 1 to 6as appropriate.

Embodiment Mode 8

In this embodiment mode, an example of a liquid crystal display devicein which deterioration of liquid crystal caused in a manufacturingprocess is prevented and which has good adhesion between substrates,high reliability and high image quality, and the manufacturing methodthereof will be described. Specifically, a liquid crystal display moduleusing the present invention will be described.

This embodiment mode will be described with reference to FIGS. 10A and10B.

FIGS. 10A and 10B illustrate a structural example of a liquid crystaldisplay device (a liquid crystal display module) using an elementsubstrate 2600 manufactured by application of the present invention.

FIG. 10A illustrates an example of a liquid crystal display module, inwhich the element substrate 2600 and a counter substrate 2601 areattached to each other with a sealant 2602 using a plurality ofprojections 2615 a, 2615 b, 2615 c and 2615 d, and a pixel portion 2603including a TFT, or the like, a liquid crystal layer 2604 and a coloredlayer 2605 are provided therebetween to form a display region. Thecolored layer 2605 is necessary to perform color display. In the case ofthe RGB system, respective colored layers corresponding to colors ofred, green, and blue are provided for corresponding pixels. The outerside of the element substrate 2600 and the counter substrate 2601 isprovided with a polarizing plate 2606, a polarizing plate 2607 and adiffuser plate 2613. A light source includes a cold cathode tube 2610and a reflector plate 2611. A circuit board 2612 is connected to theelement substrate 2600 by a flexible wiring board 2609. Externalcircuits such as a control circuit and a power supply circuit areincorporated in the circuit board 2612. The polarizing plate and theliquid crystal layer may be stacked with a retardation plate interposedtherebetween.

The liquid crystal display device in FIGS. 10A and 10B is an example inwhich the polarizing plate 2606 are provided on an outer side of thecounter substrate 2601 (a viewing side), and the colored layer 2605 areprovided on an inner side of the counter substrate 2601. However, thepolarizing plate 2606 may be provided on the inner side of the countersubstrate 2601 (on the liquid crystal side), and the colored layer 2605may be provided on an outer side of the counter substrate. Thestacked-layer structure of the polarizing plate 2606 and the coloredlayer 2605 is not limited to that of FIG. 10A and may be determined asappropriate depending on materials of the polarizing plate 2606 and thecolored layer 2605 or conditions of a manufacturing process.

Similarly to Embodiment Mode 1, in this embodiment mode using thepresent invention, a surface of an uncured sealant provided for thecounter substrate 2601 is cured by the first cure treatment beforedropping liquid crystal in a method for manufacturing a liquid crystaldisplay device in which the liquid crystal is dropped by a droppingmethod to form the liquid crystal layer. After dropping the liquidcrystal, the counter substrate 2601 and the element substrate 2600 areattached to each other with the liquid crystal interposed therebetween.Then, the sealant is subjected to a second cure treatment to be curedwholly. In the present invention, the element substrate 2600 has theplurality of projections 2615 a, 2615 b, 2615 c, 2615 d in a sealantadhesive region. The counter substrate 2601 and the element substrate2600 are attached to each other with the liquid crystal interposedtherebetween so that the plurality of projections 2615 a, 2615 b, 2615 cand 2615 d are implanted in the sealant provided for the countersubstrate 2601.

Since a surface of the sealant is cured by the first cure treatment(also referred to as a temporary cure treatment), the liquid crystal isnot in contact with the uncured sealant. Accordingly, contamination ofthe liquid crystal due to the uncured sealant can be prevented.Therefore, reduction in reliability of the liquid crystal display devicecaused by deterioration of the liquid crystal can be prevented. Theliquid crystal display device with reduced display unevenness, a reduceddisplay defect and high image quality can be realized.

In this embodiment mode, although the surface of the sealant is cured bythe first cure treatment, an inside of the sealant is still in anuncured state in which adhesiveness is high. Since a sealant adhesiveregion of the element substrate 2600 is provided with the plurality ofprojections 2615 a, 2615 b, 2615 c and 2615 d, when the countersubstrate 2601 and the element substrate 2600 are attached to eachother, the plurality of projections 2615 a, 2615 b, 2615 c and 2615 dare implanted in the sealant. The projections 2615 a, 2615 b, 2615 c and2615 d physically destroy the surface of the sealant of whichadhesiveness is lowered by cure treatment and penetrate the inside ofthe sealant, so that the projections can be in contact with the uncuredsealant with high adhesiveness. Accordingly, the second cure treatmentis performed in a state where the plurality of projections 2615 a, 2615b, 2615 c and 2615 d is implanted in the sealant 2602 and the sealant iswholly cured, whereby the counter substrate 2601 and the elementsubstrate 2600 can be attached firmly to each other and can stick toeach other.

Adhesiveness between the counter substrate 2601 and the elementsubstrate 2600 can be improved and reliability of the liquid crystaldisplay device can be improved.

The insulating layer serving as an alignment film can be formed usingpolyimide, polyamide, or the like. The insulating layer can serve as thealignment film by being subjected to rubbing treatment, but it is notlimited as long as the insulating layer can serve as an alignment filmwhich aligns liquid crystal molecules in one direction. Lightirradiation or heat treatment may be performed on the insulating layerto form an alignment film.

As the sealant, typically, a material containing a visible light curableresin, an ultraviolet curable resin, or a thermosetting resin can beused. For example, an epoxy resin such as a bisphenol-A liquid resin, abisphenol-A solid resin, a bromine-containing epoxy resin, a bisphenol-Fresin, a bisphenol-AD resin, a phenol resin, a cresol resin, a novolacresin, a cycloaliphatic epoxy resin, an Epi-Bis type epoxy resin, aglycidyl ester resin, a glycidyl amine resin, a heterocyclic epoxyresin, or a modified epoxy resin can be used.

When an element substrate over which a semiconductor element such as athin film transistor is formed is used, the liquid crystal may bedropped to the element substrate. Alternatively, the sealant may beprovided for a counter substrate provided with a color filter, a blackmatrix, or the like and the liquid crystal may be dropped to the countersubstrate. Accordingly, the sealant may be provided for either theelement substrate 2600 or the counter substrate 2601 and the liquidcrystal may be dropped to either the element substrate 2600 or thecounter substrate 2601. In this embodiment mode, since the sealant isprovided for the counter substrate 2601 and the liquid crystal isdropped to the counter substrate 2601, the plurality of projections 2615a, 2615 b, 2615 c and 2615 d is provided in the sealant adhesive regionof the element substrate.

The liquid crystal display module can employ a TN (Twisted Nematic)mode, an IPS (In-Plane-Switching) mode, an FFS (Fringe Field Switching)mode, an MVA (Multi-domain Vertical Alignment) mode, a PVA (PatternedVertical Alignment) mode, an ASM (Axially Symmetric aligned Micro-cell)mode, an OCB (Optical Compensated Birefringence) mode, an FLC(Ferroelectric Liquid Crystal) mode, an AFLC (Anti Ferroelectric LiquidCrystal) mode, or the like.

FIG. 10B illustrates an example of applying an FS method to the liquidcrystal display module of FIG. 10A, so that this liquid crystal displaymodule is an FS-LCD (Field Sequential-LCD). The FS-LCD performs red,green, and blue light emissions in one frame period. Color display canbe performed by composing an image by a time division method. Also,emission of each color is performed using a light-emitting diode, a coldcathode tube, or the like; hence, a color filter is not required. Thereis no necessity for arranging color filters of three primary colors andlimiting a display region of each color. Display of all three colors canbe performed in any region. On the other hand, since light emission ofthree colors is performed in one frame period, high speed response ofliquid crystal is needed. When an FS system is applied to the liquidcrystal display device of the present invention, a liquid crystaldisplay device or a liquid crystal television device having higherperformance and high image quality can be completed.

An optical response speed of the liquid crystal display module isincreased by narrowing a cell gap of the liquid crystal display module.Alternatively, the optical response speed can be increased by loweringthe viscosity of the liquid crystal material. The optical response speedcan be further increased by an overdrive method in which an appliedvoltage is increased (or decreased) only for a moment.

The liquid crystal display module of FIG. 10B is a transmissive liquidcrystal display module, in which a red light source 2910 a, a greenlight source 2910 b, and a blue light source 2910 c are provided aslight sources. A control portion 2912 is provided for the light sources,to separately control the red light source 2910 a, the green lightsource 2910 b, and the blue light source 2910 c to be turned on or off.The light emission of each color is controlled by the control portion2912, and light enters the liquid crystal to compose an image using thetime division, thereby performing color display.

Accordingly, in the liquid crystal display device of this embodimentmode using the present invention, deterioration of the liquid crystalwhich is caused in a manufacturing process can be prevented. Further,the liquid crystal display device with good adhesion between substrates,high reliability and high image quality can be realized. Moreover, sucha liquid crystal display device with high reliability and high imagequality can be manufactured with high productivity.

This embodiment mode can be combined with any of Embodiment Modes 1 to 8as appropriate.

Embodiment Mode 9

A television set (also referred to as simply a TV or a televisionreceiver) can be completed using a liquid crystal display device formedin accordance with the present invention. FIG. 15 is a block diagramshowing a main structure of a television set.

As for the display panel, there are the following cases: a case in whichonly a pixel portion 901 is formed as shown in FIG. 15 and a scanningline driver circuit 903 and a signal line driver circuit 902 are mountedby a TAB method as shown in FIG. 13B; a case in which the scanning linedriver circuit 903 and the signal line driver circuit 902 are mounted bya COG method as shown in FIG. 13A; a case in which a TFT is formed asshown in FIG. 13B, the pixel portion 901 and the scanning line drivercircuit 903 are formed over a substrate, and the signal line drivercircuit 902 is separately mounted as a driver IC; a case in which thepixel portion 901, the signal line driver circuit 902, and the scanningline driver circuit 903 are formed over a substrate as shown in FIG.12C; and the like. The display panel may have any of the structures.

As another external circuit in FIG. 15, a video signal amplifier circuit905 which amplifies a video signal among signals received by a tuner904, a video signal processing circuit 906 which converts the signalsoutputted from the video signal amplifier circuit 905 into chrominancesignals corresponding to respective colors of red, green, and blue, acontrol circuit 907 which converts the video signal into an inputspecification of the driver IC, and the like are provided on an inputside of the video signal. The control circuit 907 outputs signals toboth a scanning line side and a signal line side. In the case of digitaldrive, a signal dividing circuit 908 may be provided on the signal lineside and an input digital signal may be divided into m pieces andsupplied.

An audio signal among signals received by the tuner 904 is sent to anaudio signal amplifier circuit 909 and is supplied to a speaker 913through an audio signal processing circuit 910. A control circuit 911receives control information of a receiving station (receptionfrequency) or sound volume from an input portion 912 and transmitssignals to the tuner 904 and the audio signal processing circuit 910.

A television device can be completed by incorporating the display moduleinto a chassis as illustrated in FIGS. 16A and 16B. When a liquidcrystal display module is used as a display module, a liquid crystaltelevision device can be manufactured. In

FIG. 16A, a main screen 2003 is formed by using the display module, anda speaker portion 2009, an operation switch, and the like are providedas its accessory equipment.

Thus, a television device can be completed in accordance with thepresent invention.

A display panel 2002 is incorporated in a chassis 2001, and general TVbroadcast can be received by a receiver 2005. When the display device isconnected to a communication network by wired or wireless connectionsvia a modem 2004, one-way (from a sender to a receiver) or two-way(between a sender and a receiver or between receivers) informationcommunication can be performed. The television device can be operated byusing a switch built in the chassis 2001 or a remote control unit 2006.A display portion 2007 for displaying output information may also beprovided in the remote control device 2006.

Further, the television device may include a sub screen 2008 formedusing a second display panel so as to display channels, volume, or thelike, in addition to the main screen 2003. In this structure, the mainscreen 2003 and the sub screen 2008 can be formed using the liquidcrystal display device of the present invention. In accordance with thepresent invention, a liquid crystal display device with high reliabilitycan be manufactured even when a large-sized substrate is used and alarge number of TFTs or electronic components are used.

FIG. 16B illustrates a television device having a large-sized displayportion, for example, a 20-inch to 80-inch display portion. Thetelevision device includes a chassis 2010, a display portion 2011, aremote control device 2012 that is an operation portion, a speakerportion 2013, and the like. This embodiment mode of the presentinvention is applied to manufacturing of the display portion 2011. Sincethe television device in FIG. 1613 is a wall-hanging type, it does notrequire a large installation space.

Naturally, the present invention is not limited to the televisiondevice, and can be applied to various use applications as a large-sizeddisplay medium such as an information display board at a train station,an airport, or the like, or an advertisement display board on thestreet, as well as a monitor of a personal computer.

This embodiment mode can be freely combined with any of Embodiment Modes1 to 8 as appropriate.

Embodiment Mode 10

Examples of electronic appliances in accordance with the presentinvention are as follows: a television device (also referred to assimply a television, or a television receiver), a digital camera, adigital video camera, a cellular telephone device (simply also referredto as a cellular phone or a cell-phone), a mobile information terminalsuch as PDA, a portable game machine, a computer monitor, a computer, asound reproducing device such as a car audio system, an imagereproducing device including a recording medium, such as a home-use gamemachine, and the like. Further, the present invention can be applied tovarious game machines having a liquid crystal display device such as apachinko machine, a slot machine, a pinball machine, and a large-scaledgame machine. Specific examples thereof are described with reference toFIGS. 17A to 17F.

A portable information terminal device illustrated in FIG. 17A includesa main body 9201, a display portion 9202, and the like. The liquidcrystal display device of the present invention can be applied to thedisplay portion 9202. As a result, a portable information terminaldevice which can display a high-quality image with high reliability canbe provided.

A digital video camera illustrated in FIG. 17B includes a displayportion 9701, a display portion 9702, and the like. The liquid crystaldisplay device of the present invention can be applied to the displayportion 9701. As a result, a digital video camera which can display ahigh-quality image with high reliability can be provided.

A cellular phone illustrated in FIG. 17C includes a main body 9101, adisplay portion 9102, and the like. The liquid crystal display device ofthe present invention can be applied to the display portion 9102. As aresult, a cellular phone which can display a high-quality image withhigh reliability can be provided.

A portable television device illustrated in FIG. 17D includes a mainbody 9301, a display portion 9302 and the like. The liquid crystaldisplay device of the present invention can be applied to the displayportion 9302. As a result, a portable television device which candisplay a high-quality image with high reliability can be provided. Theliquid crystal display device of the present invention can be applied toa wide range of television devices ranging from a small-sized televisiondevice mounted on a portable terminal such as a cellular phone, amedium-sized television device which can be carried, to a large-sized(for example, 40-inch or larger) television device.

A portable computer illustrated in FIG. 17E includes a main body 9401, adisplay portion 9402, and the like. The liquid crystal display device ofthe present invention can be applied to the display portion 9402. As aresult, a portable computer which can display a high-quality image withhigh reliability can be provided.

A slot machine illustrated in FIG. 17F includes a main body 9501, adisplay portion 9502, and the like. The liquid crystal display device ofthe present invention can be applied to the display portion 9502. As aresult, a slot machine which can display a high-quality image with highreliability can be provided.

As described above, an electronic appliance which can display ahigh-quality image with high reliability can be provided by using theliquid crystal display device of the present invention.

This embodiment mode can be combined with any of Embodiment Modes 1 to 9as appropriate.

This application is based on Japanese Patent Application serial no.2007-116293 filed with Japan Patent Office on Apr. 26, 2007, the entirecontents of which are hereby incorporated by reference.

1. A liquid crystal display device comprising: a pair of substrates; anda liquid crystal interposed between the pair of substrates by using asealant, wherein a plurality of projections provided for one of the pairof substrates is implanted in the sealant; and wherein a material of theplurality of projections is different from that of the one of the pairof substrates.
 2. The liquid crystal display device according to claim1, wherein the sealant includes an ultraviolet curing resin.
 3. Theliquid crystal display device according to claim 1, wherein the sealantincludes a thermosetting resin.
 4. The liquid crystal display deviceaccording to claim 1, wherein the plurality of projections has a pyramidshape.
 5. The liquid crystal display device according to claim 1,wherein the plurality of projections has a triangle pole shape, andwherein one surface of the plurality of projections is in contact withthe one of the pair of substrates.
 6. A liquid crystal display devicecomprising: a first substrate having a pixel region and a sealantadhesive region; a second substrate having a counter electrode; thepixel region comprising: a thin film transistor; an insulating film overthe thin film transistor; a pixel electrode over the insulating film,the pixel electrode being electrically connected to the thin filmtransistor; and a liquid crystal between the pixel electrode and thecounter electrode; the sealant adhesive region comprising: a sealant;and a plurality of projections in the sealant, wherein a material of theplurality of projections is different from that of the first and secondsubstrates.
 7. The liquid crystal display device according to claim 6,wherein the sealant includes an ultraviolet curing resin.
 8. The liquidcrystal display device according to claim 6, wherein the sealantincludes a thermosetting resin.
 9. The liquid crystal display deviceaccording to claim 6, wherein the plurality of projections has a pyramidshape.
 10. The liquid crystal display device according to claim 6,wherein the plurality of projections has a triangle pole shape, andwherein one surface of the plurality of projections is in contact withthe second substrate.